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GRADUATE RESEARCH SYMPOSIUM

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ANNUAL GRADUATE STUDENT SYMPOSIUM  |   Global Change Center

Each year, Ph.D. students in the Interfaces of Global Change IGEP present their research findings during a full-day research symposium held on campus. This event provides a forum for students and faculty to interact and explore connections among research programs, build comradery, and celebrate our students’ research accomplishments. .

The symposium typically features a keynote lecture, student presentations, a poster session, and a reception. All Global Change Center affiliated faculty and students are invited to attend.

Explore previous and upcoming schedules below.

 

Bee on Flower

Interfaces of Global Change Graduate Research Symposium

April 22, 2022

The Seventh Annual Interfaces of Global Change (IGC) Graduate Research Symposium is scheduled for April 22, 2022.  This annual meeting provides a space to showcase and celebrate the important and impressive work of the IGC Ph.D. Fellows.  It’s also a time for Fellows and GCC faculty to interact and explore connections between labs across campus.  This year’s symposium agenda will include platform presentations, poster viewing sessions and a keynote speaker selected by the IGC Graduate Student Organization.

Fellows who are in their 2nd year of the IGC program (admitted Spring 2021) are expected to present their work at the symposium in the form of a poster or platform presentation.  First year IGC Fellows have the option to present their proposed research ideas as a poster but are not required to do so.  Fellows who have presented before should be sure to submit abstracts on new research findings that differ from their prior symposium presentation(s). Awards will be given for the best platform presentations.

Due to schedule constraints the number of oral presentations will be limited to approximately 10.  Senior IGC Fellows, in their 3rd, 4th, or 5th year of study are strongly encouraged to select to give a talk.  Priority will be given to those who 1) have not presented a talk at a past IGC symposium, 2) present result-driven content and 3) present content that is interdisciplinary and relevant to global change issues.

 

FORMAT

Each abstract should contain:

  1. Title
  2. Authors and Affiliations (e.g., Department and University), presenting author denoted by an asterisk.
  3. An abstract highlighting key findings and not to exceed 250 words in length

Format example:

Hopkins, W.A.*1, Dude, T.H.E. 1,2, and Sobchak, W. 1
1 Dept. of Fish and Wildlife Conservation, Virginia Tech; 2 Dept. of Interior Room Design, University of Abides

PLATFORM TALKS: presentation max time length of 12 minutes, followed by 3 minutes for Q&A.

POSTERS: maximum poster size is 40″ x 60″.  An easel and backboard will be provided.

Schedule
Zoom Screenshot

6th Annual

Interfaces of Global Change Graduate Research Symposium

April 23, 2021
Virtual

The Sixth Annual Interfaces of Global Change (IGC) Graduate Research Symposium was held virtually over Zoom on April 23, 2021. Although the forum was a little different this year, this annual meeting provides a space to showcase and celebrate the important and impressive work of the IGC Fellows.  It’s also a time for Fellows and GCC faculty to interact and explore connections between labs across campus.  This year’s symposium agenda included 12 platform presentations, 12 research power talks, introductory videos from the 12 newest Fellows in the Spring 2021 cohort, and an overview by Fellows leading a new IGC Peer Mentoring Program.

Awards for Best Platform Presentations and Research Power Talks were selected for the top three presentations in each category. The 2021 winners were:

 

Platform Presentations

First Place Alaina Weinheimer, “Too big to see: large viruses are overlooked players in the ocean’s nutrient cycles”

Second Place Sara Cathey, “Experimental evidence that biodiversity stabilizes communities through asynchrony”

Third Place Kerry Gendreau, Daniel Smith, Joshua Rady & Isaac VanDiest, “V-SCI: Connecting science with local environmental advocacy”

Research Power Talks

First Place Mary Lofton, “Thermocline deepening deepens maximum phytoplankton biomass and affects community phytoplankton community structure in a eutrophic reservoir”

Second Place Sara Richards, “Effects of temperature on contact rates in house finches”

Third Place Korin Jones, “Community assembly in the amphibian microbiome”

Kudos to all the student participants!  Your research never ceases to inspire and give us hope for a bright future.  Thank you to the GCC Faculty and other researchers on campus who came out to show their support for the IGC Fellows!

Friday, April 23, 2021  (Finalized Detailed PDF Here)

9:00 am     Welcome, by IGC Director Bill Hopkins

9:15 am     IGC Platform Presentations Session 1

10:15 am   Break

10:30 am   IGC Platform Presentations Session 2

11:30 am   Break

12:30 pm   IGC Platform Presentations Session 3

1:30 pm     Break

2:00 pm     Research Power Talks

3:00 pm     Break

3:30 pm     Introductory Power Talks from newest IGC Fellows

3:50 pm     IGC Peer Mentoring Program Overview

4:05 pm     Best Presentation Awards Announcement

 

Authors: Carvalho, F. M.*1, Castello, L.1, Ferreira, B.2 and Power, M.3

Affiliations: 1Dept. of Fish and Wildlife Conservation, Virginia Tech; 2Dept. of Oceanography, Federal University of Pernambuco; 3Dept. of Biology, University of Waterloo

Small-scale reef fisheries are important commercial and subsistence activities that support the livelihoods of millions of people in tropical regions. Tropical marine fisheries typically target a diversity of species caught by a matching diversity of fishing gears and practices. High fishing pressure, however, often leads to the overexploitation of coral reef fish assemblages. Here, we explored how multiple fishing gears select for distinct functional traits and how they affect the function of fish assemblages inside a large multiple use MPA off northeastern Brazil. In 1,888 landing interviews with local fishers, we identified 101 species, which were categorized according to six traits: body size, schooling behavior, mobility, position in the water column, diet and period of activity. We found a low competitive interaction between different gear types, meaning there was a low overlap in trait selectivity between fishing gears. We also found direct associations between gears and fish functional traits: hooks and line targeted species that exhibit limited mobility capabilities, making these species more vulnerable to local levels of fishing effort. In contrast, nets and fish corrals targeted mobile species that exhibited a greater diversity of functional traits. Some of our results contrasted with the current literature on the topic, with differences calling for more research to clarify global patterns of trait selectivity per gear type. Our results have implications for fisheries management in northeastern Brazil: gear bans and effort caps are commonly used management measures that can foster fisheries sustainability by minimizing impacts to fish assemblage functions.

Authors: Cathey, Sara*1, Brown, Bryan2, Downing, Amy1, Liebold, Mathew3

Affiliations: 1Dept. of Biological Sciences, Virginia Tech; 2Zoology Dept., Ohio Wesleyan University; 3Dept. of Biology, University of Florida

As the variability of ecological systems increases under global change, the need to identify the mechanisms through which biodiversity stabilizes communities and ecosystems has increased. Asynchronous population dynamics that arise from species interactions and differential responses to environmental conditions may stabilize community dynamics. In a zooplankton mesocosm experiment, we tested the roles biodiversity, community composition, and environmental variability play in inducing the mechanisms that may stabilize ecological communities. As diversity increased, community-wide asynchrony increased. While the role of environmental variability was less clear, it did encourage asynchronies between one pair of dominant species. Mesocosms connected to the regional species pool via dispersal resulted in the highest levels of diversity and consequently resulted in the highest levels of asynchrony and stability. These results demonstrate that biodiversity can stabilize communities by generating asynchronous population dynamics, but that those effects are largely dependent on the specifics of community composition and how composition responds to environmental fluctuations and dispersal.

Authors: Gendreau, K.1, Smith, D.2, Rady, J.M.3, VanDiest, I.1, Weinheimer, A.1, DeHority, R.2

Affiliations: 1Dept. of Biological Sciences, Virginia Tech; 2Dept. of Biological Systems Engineering, Virginia Tech; 3Dept. of Forest Resources & Environmental Conservation, Virginia Tech

The Virginia Scientist-Community Interface (V-SCI) is a volunteer graduate student group founded in 2019 at the University of Virginia that provides non-profit organizations and advocacy groups with scientific research support. Starting in January 2020, a group of IGC fellows joined V-SCI.  The group has since expanded to include collaborators from multiple universities and independent organizations. We have since completed two reports analysing environmental impacts from the Atlantic Coast and Mountain Valley Pipelines. These reports were submitted as referenced public comments to the U.S. Fish and Wildlife Service and the U.S. Forest Service. In our comments, we identified inadequacies not recognized by relevant agencies and companies involved in the projects, including inappropriate model assumptions and underestimations of the potential impacts of sedimentation on populations of endangered species residing in the proposed pipeline pathways. V-SCI has provided the participating IGC fellows with the unique opportunity to collaborate on research that supports science-based decision-making regarding local, real world environmental issues. We learn more with each new project and the organization continues to expand in size and scope to work with a larger and more diverse set of topics.

Authors: Lakoba, Vasiliy*1,2, Lavesta C. Hand3, Lee R. Van Wychen4

Affiliations:  1School of Plant and Environmental Sciences, Virginia Tech, Blacksburg VA; 2Interfaces of Global Change Graduate Education Program, Virginia Tech, Blacksburg VA;  3Department of Crop & Soil Sciences, University of Georgia, Tifton GA; 4Weed Science Society of America, Alexandria VA

Invasive species are one of the most problematic facets of global change, whose impacts on biodiversity, human health, and national and local economies continue to accelerate in our increasingly interconnected world. Harmful species introductions, intentional or unintentional, are the focus of preventative and curative policy, which navigates a tangle of conflicting interests, stakeholders, and existing regulations. Graduate education in invasion biology increasingly strives to give future professionals a glimpse into the complexity of state, federal, and international policy affecting the regulation and funding of invasion prevention and mitigation. One way to curate such experiences is through scientific and professional societies that include science policy departments. Having completed a term as a science policy fellow with the Weed Science Society of America (WSSA) in 2020-21, the presenter (VTL) had the privilege of learning about and participating in the society’s and other invasion-focused groups’ engagement of U.S. federal agencies and policymakers. This experience included numerous meetings with society constituents, academic researchers, industry advocates, congressional staffers, and federal scientists. Duties as a science policy fellow included drafting comments on behalf of WSSA regarding proposed documents and decisions for the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), the Environmental Protection Agency, and the Department of the Interior. Despite its virtual format due to the global pandemic, this immersive fellowship profoundly complemented the policy-oriented portions of the IGC curriculum. Pursuing similar experiences through relevant disciplinary societies could help other IGC fellows assess their own interest in pursuing careers in science policy.

Authors: Lane, Samuel J.*1, Michael G. Emmerson2, Isaac J. VanDiest1, Catherine Hucul1, Michelle L. Beck3, Scott Davies4, Elizabeth R. Gilbert5,6, Kendra B. Sewall1,6

Affiliations: 1Virginia Tech, Department of Biological Sciences; 2Quen Mary University of London, School of Biological and Chemical Sciences; 3Rivier University, Department of Biology; 4Quinnipiac University, Department of Biological Sciences; 5Virginia Tech, Department of Animal and Poultry Sciences; 6Virginia Tech, School of Neuroscience

Individuals in urban habitats experience frequent disturbances and are expected to respond efficiently and recover quickly from challenges to persist in these novel habitats. The glucocorticoid stress response is a physiological response to a stressor during which glucocorticoid concentration increases in order to activate behavioral and physiological mechanisms to recover homeostasis. Differences in the duration of glucocorticoid secretion are modulated by the efficiency of negative feedback mechanisms, which is achieved primarily through the binding of glucocorticoid receptors (GRs) in the hippocampus by glucocorticoids. We investigated if male song sparrows (Melospiza melodia) in urban habitats show more efficient negative feedback of the glucocorticoid stress response than their rural counterparts. Males from each habitat were exposed to restraint stress to increase corticosterone, the primary avian glucocorticoid, then injected with either saline or a synthetic glucocorticoid (dexamethasone), to induce a negative feedback response. Additionally, we quantified GR mRNA in the hippocampus using qPCR in a separate cohort of birds. Our results show that dexamethasone suppressed relative corticosterone concentration below that of saline, but no habitat differences in response to dexamethasone were detected. We found that stress induced corticosterone was significantly lower in urban birds, however previous research has shown variation in stress induced levels of glucocorticoids across years in this population. Urban song sparrows did have lower hippocampal mRNA levels of GR than rural song sparrows. Urbanization therefore does not consistently affect the glucocorticoid stress response, but can cause structural changes in the hippocampus, the functional effects of which remain to be elucidated.

Authors: McNeill, Noah*1 and Walters, J.R.1

Affiliations: 1Virginia Tech, Department of Biological Sciences

Prior to European expansion, pine-savanna comprised two-thirds of the Atlantic Coastal Plain from Virginia to Texas, a habitat historically dominated by Longleaf Pine (Pinus palustris). Over roughly three-hundred years, ninety-five percent of the pine-savanna was eliminated by the resin industry, agriculture, and logging, with partial reforesting by twentieth century Loblolly Pine (Pinus taeda) plantations. In order to investigate the impact of these massive land cover shifts on pine-savanna wildlife, I am studying the foraging and multi-species flocking behavior of the Brown-headed Nuthatch (Sitta pusilla), which feeds heavily on both Longleaf and Loblolly seeds when available. By comparing rates of nuthatch pine foraging and multi-species flocking at divergent sites (Marine Corps Base Camp Lejeune and the Sandhills Gamelands, NC), I demonstrate examples of a pine-savanna species’ resilience despite shifting habitat parameters. As recent pine-savanna reconstruction efforts and the increasing effects of climate change may serve to reduce Loblolly Pine prevalence, I also expound upon ways that pine-savanna wildlife could be impacted in the future.

Authors: Novak, Leah D.*1, Walters, J.R.1, and Dylan Kesler2  

Affiliations: 1Biological Sciences, Virginia Tech; 2The Institute for Bird Populations

Many cooperative breeders show similar dispersal syndromes, including reliance on frequent forays outside the natal territory prior to dispersal to explore the surrounding habitat and make informed decisions on where to disperse.  These species are highly territorial and defend all-purpose territories year-round that contain limited resources required for breeding and survival, which limits the habitat available to dispersing individuals.  Climate change is of special concern for these habitat specialists that have limited capacity to shift their range, and hence must adapt in place or perish.  The cooperatively breeding red-cockaded woodpecker, a federally listed endangered species endemic to fire dependent pine savannah of the southeastern United States, is one such species.  Productivity of this species is increasing in the northern part of its range, but declining in the southwestern portion, showing current effects of climate change.  Understanding how dispersing individuals explore and interact with the landscape may enable managers to reduce dispersal-related mortality and increase functional habitat connectivity.  Male juveniles can adopt one of two distinct, condition-dependent dispersal syndromes: they can delay dispersal and remain on their natal territory as non-breeding helpers (dominant strategy) or disperse their first year in search of territories with open breeding positions (subordinate strategy).  We radio-tagged and followed dominant and subordinate juvenile male pairs from the same brood from winter to the start of the breeding season to observe foray-related dispersal behavior.  All radio-tagged males spent time on forays away from their families, although subordinate males forayed significantly more than dominant males.  On forays, males foraged significantly less than when with their families, traveled significantly more, and altered their patterns of movement dependent on many habitat and social cues.  For subordinate males, foraying culminated into a move to a new location (dispersal) before the beginning of the breeding season, but dominant males remained with their families.  Overall, pre-dispersal foraying dominates the process of dispersal and thus is a key element in determining how these birds move in their environment, and how landscape structure influences juvenile movement and mortality.

Authors: Semel, M.A.*1, Ratovoson, J.C.2, and Moore, I.T.1  

Affiliations: 1Biological Sciences, Virginia Tech; 2Dept. of Animal Biology and Conservation, University of Antananarivo

Protected areas and conservation planning require careful consideration of target species resource needs over space and time. Understanding animal movement and foraging patterns is crucial to developing management plans across naturally and anthropogenically dynamic landscapes. While Madagascar currently has extensive protected area coverage, most protected areas were created to encompass large, remaining forests rather than out of consideration for target species resource needs. Specifically, golden-crowned sifakas (Propithecus tattersalli) are a critically endangered lemur species endemic to forest fragments across a range of forest types in one protected area in northeastern Madagascar, but little is known about their space or resource needs. To better understand sifaka space use and foraging behavior for developing management plans, we combined individual animal follows with Dynamic Brownian Bridge Movement Models. We also examined the influence of abiotic, biotic, and anthropogenic factors on sifaka home range size and foraging patterns. We found that home range size differed between seasons (rainy or dry), with increased core area use and movement in the rainy season. Human infrastructure also played a role in sifaka foraging behavior as lemur groups in humid and dry deciduous forests avoided road networks and human villages when selecting foraging resources. Our study illustrates the importance of understanding seasonal patterns, forest type, and human disturbance when determining dynamic primate spatial needs. Accounting for behavioral variation in response to these factors will allow conservationists to best manage protected area coverage (i.e., via reforestation) for sifakas in light of ongoing and future climate and land cover change.

Authors: Seo, Hye-jeong*1; Todd Schenk1

Affiliations: 1School of Public and International Affairs, Virginia Tech

This study explores how local news media covers environmental risks and what factors contribute to the inclusion of scientific information in that reporting. We conducted a content analysis of news articles about environmental issues associated with the Radford Army Ammunition Plant (RAAP), in Radford, VA. We coded 116 articles published between 2000 and 2019, with four coding criteria: the inclusion of scientific information, sources of scientific information, claims-makers, and risk assertions. The preponderance of news articles quote claims from RAAP officials (44.8%), followed by State officials (32.8%), community activists (25.0%), and others (17.2%). Only 35.3% of articles include scientific information and the source of such information is typically government officials and reports (54.9% of scientific claims). While all articles coded focus on environmental issues, most (59.5%) do not include explicit risk assertions (i.e., claims of risks present and/or their absence). Logistic regression analysis indicates that when an article includes claims made by state officials, it is 4.5 times more likely to include scientific information. When an article includes claims made by community activists, it is 84% less likely to include scientific information. When an article explicitly asserts the existence of environmental risks, it is 12 times more likely to include scientific information. This paper further explores possible reasons why certain sources are cited and information claims reproduced in the news media.

Authors: Silknetter, Samuel*1, Abigail L. Benson2, Jennifer A. Smith3, Meryl C. Mims1

Affiliations: 1Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA; 2U.S. Geological Survey, Science Analytics and Synthesis, Denver, CO, USA; 3Department of Environmental Science & Ecology, University of Texas at San Antonio, San Antonio, TX, USA

Assessing sensitivity of freshwater species to climate change is essential to prioritizing conservation efforts. Sensitivity can be evaluated across multiple species by comparing measurable attributes such as traits, range size, and climate niche breadth; however, the degree to which spatial scale influences outcomes of such assessments is unclear. The effects of spatial extent may cause scale dependencies that decouple the outcomes of analyses performed at regional and national scales. To address this knowledge gap, we assessed intrinsic climate sensitivity for 144 native freshwater fishes of the United States using publicly available occurrence data from the Global Biodiversity Information Facility (GBIF). Results indicate that for regional species pools, mean sensitivity values did not differ between assessments at national and regional scales. However, regional assessments revealed that the intrinsic sensitivity of individual species often varied significantly between geographic regions in which they occur. This suggests that species’ intrinsic sensitivity is strongly influenced by the scale or extent of the assessment. As conservation practitioners consider regional management actions for at-risk species, it is vital to ensure that the vulnerability assessments informing those decisions have been conducted at the appropriate scale.

Authors: Wang, Suwei*1,2, Molly B. Richardson3, Connor Y.H. Wu4, Benjamin F. Zaitchik5, Julia M. Gohlke6

Affiliations: 1Translational Biology, Medicine, and Health (TBMH), Virginia Tech, Blacksburg, VA; 2Department of Population Health Sciences, Virginia Tech, Blacksburg, VA; 3Division of Preventive Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, AL; 4Department of Geospatial Informatics, Troy University, Troy, AL; 5Department of Earth & Planetary Sciences, Johns Hopkins University, Baltimore, MD

Previous studies have indicated high temperature/humidity is a barrier to meeting physical activity (PA) guidelines. As heat wave days increase with climate change, characterizing changes in PA and implications for chronic disease health outcomes are needed. Evidence shows time spent outdoors is positively associated with PA. We hypothesized even a small amount of increased outdoor time in summer may promote PA while bringing minimally increased heat exposure. Urban and rural participants (total = 180) were asked to perform normal activities on Days 1-2 (baseline) and spend an additional 30 minutes outdoors on Days 3-7 (intervention). Participants wore thermometers clipped to their shoes to estimate individually experienced heat index (HI) and pedometers. Linear mixed models were fitted to estimate relationships between PA measured by pedometer steps and individually experienced HI on baseline versus intervention days, accounting for ambient conditions (HI, rain, wind speed). Participants carried out the intervention on 736 (83%) person-days. Rain, heat, and time conflicts were top self-reported reasons for non-compliance. Participants on average walked 637 (95%CI 83-1192) more steps during intervention compared to baseline. Participants had a 0.59°C (95%CI 0.30-0.88) lower mean individually experienced heat index during intervention, accounting for ambient conditions and individual-level factors. The intervention benefit was greater in rural residents who were less active at baseline, compared to urban residents. This study presents methods for estimating how PA is related to heat exposure and time outdoors, integrating wearable sensor data and ambient weather conditions.

Authors: Weinheimer, A. R.*1, Aylward, F. O.1

Affiliations: 1Dept. of Biological Sciences, Virginia Tech

While several viruses can cause deadly human diseases, such as COVID-19, many viruses do not. In the ocean, viruses infect microbes like algae and bacteria, killing up to 15% of bacteria each day. By infecting microbes, viruses release their host’s organic material into the ocean, which impacts food webs and nutrient cycles, such as the carbon pump. How we study viruses in the ocean tends to bias toward smaller ones. We use filters to remove cells from seawater samples and concentrate for virus particles. However, exceptionally large viruses have recently been uncovered in environments around the world. These large viruses can be even bigger than some bacterial and algal cells. One group of these viruses is called jumbo phages. Jumbo phages infect bacteria and are four times the size of most known phages. Because our methods bias against jumbo phages, they are thought to be rare in nature. In this study, we sought to determine how rare jumbo phages are in the ocean versus the extent that current methods’ overlook them. We searched for jumbo phages in metagenomic data (DNA sequences of all organisms in a sample) deriving from seawater that was enriched for bacteria rather than for viruses, and we uncovered 91 jumbo phages present throughout Earth’s ocean. Many of these phages are highly active and encode genes important to nutrient cycles that their microbial hosts drive. Our results suggest that how we study viruses must be revisited to better understand the impact of viruses on ecosystem health.

Authors: Alfonso, Camilo*1, Moore, Ignacio1

Affiliations: 1Dept. of Biological Sciences, Virginia Tech

Manakins are neotropical birds with a polygynous mating system where males aggregate in a specific area (lek) to court females, and direct aggressive interactions are rarely seen. As such, manakins are often considered non-territorial. Moreover, in some manakins species, males form coalitions with other males to perform coordinated courtship displays. While existing research has explored these social coalitions and cooperative behavior in manakins, the behavioral response to territorial intrusions by novel males is not well understood. To understand territorial behavior in manakins, we challenged territorial males to simulated territorial intrusions. We conducted these challenges in two species on manakins that differ in their social systems. First, we investigated the wire-tailed manakin (Pipra filicauda), where males perform cooperatively coordinated displays with other males and queue for future territorial positions. Subsequently, we investigated the red-capped manakin (Ceratopipra mentalis), which has no cooperative behavior, but males can approach other males to share perches but display little aggression. We tested aggression in these two species by introducing a taxidermic mount intruder onto a territorial male and quantifying the individual’s behavioral response. While males of both species responded aggressively to the territorial intrusion, we found no significant differences in the aggression scores between the species. We concluded that while manakins’ social organization includes a high tolerance to neighbor males, and in some species, males even cooperate, aggression and territoriality are still present, at least in these two species.

Authors: Bretz, Kristen A.*1, Alexis Jackson1, Sumaiya Rahmen1, Jonathon Monroe1, and Erin R. Hotchkiss1

Affiliations: 1Dept. of Biological Sciences, Virginia Tech

The heterogeneity of CO1 and CH4 sources within and across watersheds presents a challenge to understanding the contributions of different ecosystem types to stream corridor carbon cycling. Stream carbon fluxes integrate biogeochemical processes from their contributing valleys and upstream corridors. Changing hydrology and diverse landscape patches (e.g., surface, subsurface, and riparian) can have dynamic influences on stream corridor greenhouse gas emissions. To identify patterns and sources of carbon emissions across stream corridors, we measured gas concentrations and fluxes over 2 summers at Coweeta Hydrologic Laboratory, NC. We sampled CO2 and CH4 along four streams (including flowing and dry channels), adjacent wetlands, and riparian hillslopes. Stream CO2 concentrations varied as much over space as they did time (550-2500 μatm), and all streams were sources of CO2 to the atmosphere (median from all stream reaches = 93.9 mmol m-2d-1). Streams were sources or sinks of CH4 depending on sampling location (-0.0001 to 0.158 mmol m-2d-1). Hillslopes were sources of CO2 (median 259 mmol m-2d-1) and sinks of CH4 (-0.086 mmol m-2d-1); stream dry beds were sources of both gases (median 62 mmol CO2 m-2d-1 and 0.003 mmol CH4 m-2d-1). Wetlands were consistently sources of CO2 (median 211 mmol CO2 m-2d-1); however, wetland CH4 emissions were highly heterogeneous (range 0 – 2713 mmol m-2d-1). Ongoing work seeks to integrate stream discharge with high-frequency dissolved CO2 sensor data with within-reach spatial CO2 data to identify spatiotemporal patterns of variation. Future expected hydrologic and climatic extremes will change carbon cycling through watersheds. A better understanding of carbon fluxes from diverse habitat patches within and between stream corridors will improve our quantifications of freshwater contributions to landscape and regional carbon emissions as ecosystems respond to global change.

Authors: Brousseau, J.J.*1, Stern, M.J.1, and Lemaire, R.H.2

Affiliations: 1Dept. of Forest Resources and Environmental Conservation, Virginia Tech; 2Center for Public Administration and Policy, Virginia Tech

Networks can be influential in tackling complex, multi-stakeholder problems by fostering learning and the development of innovative practices. Assessing the structure of social networks can provide insight into how relationships influence outcomes. Social network maps are increasingly employed in environmental management to identify strengths and weaknesses in the existing network and how these areas may influence future collaborations. Social network maps also represent one form of a boundary object, which are materials or abstract artifacts that bridge the gaps between social worlds and can facilitate communication and learning across groups. In this presentation, we explore how social network maps may be used as tools to identify opportunities for and barriers to collaboration in adaptation planning. We will study the networks of entities working on climate adaptation in eight communities across the US as they incorporate adaptation strategies in their general plan updates. To create the social network maps, survey data will be collected on the pre-existing relationships of workshop participants. The maps will be presented to participants via an interactive, website application and incorporated as the networks consider how to implement proposed adaptation strategies. The network maps and website will be evaluated through periodic surveys and interviews after the tool is first introduced. Feedback from participants and the research team will be incorporated to improve the website and mapping session with each successive community. If this is a helpful tool, it could have implications for the future of adaptation planning, as well as tackling other complex, multi-stakeholder issues.

Authors: Burt, M.A.*1, Whitehead, S.R.1, Haddad, N.2,3, and Resasco, J.4

Affiliations: 1Department of Biological Sciences, Virginia Tech; 2W.K. Kellogg Biological Station Long-Term Ecological Research, Michigan State University; 3Department of Integrative Biology, Michigan State University; 4Department of Ecology and Evolutionary Biology, University of Colorado

The loss and fragmentation of habitats are two of the biggest threats to biodiversity. Populations of organisms remaining in fragmented landscapes persist in smaller and more isolated pieces of habitat surrounded by human land-use. Corridors, strips of habitat reconnecting isolated habitat fragments, are used by land managers to mitigate the effects of isolation caused by fragmentation. Although much work has been done to understand the effects of corridors on seed dispersal by vertebrates, less is known about how corridors affect plants relying on nonvertebrate seed dispersers such as ants. To understand how habitat connectivity and edge effects impact ant seed dispersal, we conducted ant community sampling with pitfall traps and observations of seed removal by ants from depots in a landscape-scale experiment that manipulated connectivity (via corridors) and amount of edge across habitat patches. We asked: (1) How is seed dispersal by ants affected by connectivity and edge effects?, and (2) Are these effects mediated by changes in (a) ant community composition or (b) ant behavior? While we found no effect of connectivity and edges on the number of seeds ants dispersed or the number of ant species dispersing seeds, we did find that ants moved seeds about five times further in fragments connected with corridors. This effect was only present in the interior of fragments and did not appear to depend on the identity of ant species moving seeds. Overall, this research suggests that habitat connectivity can have important effects on the quality of seed dispersal by ants.

Authors: Gendreau, Kerry L.1*, Valerie L. Buxton1, Chloe E. Moore1, Meryl C. Mims1

Affiliations: 1Department of Biological Sciences, Virginia Tech

Hydroperiod, or the amount of time a lentic waterbody contains water, shapes communities of aquatic organisms. Precise measurement of hydroperiod features such as inundation timing and duration can help predict community dynamics and ecosystem stability. In areas defined by high spatial and temporal variability, fine-scale temporal variation in inundation timing and duration may drive community structure, but that variation may not be captured using common approaches including remote sensing technology. Here, we provide methods to accurately capture inundation timing by fitting hidden Markov models to measurements of daily temperature standard deviation collected from temperature loggers. We describe a rugged housing design to protect loggers from physical damage and apply our methods to a group of intermittent ponds in southeastern Arizona, showing that initial pond inundation timing is highly variable across a small geographic scale (~50km2). We also compare a 1-logger (pond only) and 2-logger (pond + control) design and show that, although a single logger may be sufficient to capture inundation timing in most cases, a 2-logger design can increase confidence in results. These methods are cost-effective and show promise in capturing variation in intraregional inundation timing that may have profound effects on aquatic communities, with implications for how these communities may respond to hydroperiod alteration from a changing climate.

Authors: Hoffman, D.K.*1, Hancox, P.J.2, Nesbitt, S.J.1

Affiliations: 1Department of Geosciences, Virginia Tech; 2Evolutionary Studies Institute, University of the Witwatersrand

Few events change global ecosystems as rapidly and irreversibly as mass extinctions, which lead to changes in the dominance and diversity of major groups of organisms.  The end-Permian mass extinction (EPME) decimated ecosystems globally and enabled the archosauromorph reptiles (crocodylians, birds, and their closest relatives) to dominate terrestrial environments. Previous work has shown that marine ecosystems took 8-9 million years to recover from the EPME and hypothesized terrestrial recovery was also delayed. However, the scarcity of terrestrial Early Triassic fossil assemblages limits reconstruction of ecological recovery, preventing determining if this delayed recovery is an accurate signal, or the result of preservation bias. The Driefontein locality from the Lower Triassic of South Africa preserves a rich vertebrate assemblage. As articulated specimens are rare in the Driefontein assemblage, we used teeth, isolated and within jaws, to interpret diet of these reptiles. To visualize tooth shape, we collected qualitative character scorings from 111 isolated (of thousands) teeth, ordinated using non-metric multi-dimensional scaling (NMDS). The isolated teeth reveal four new carnivorous/insectivorous morphotypes (categories of teeth based on overall shape) and two morphotypes potential herbivorous morphotypes. The presence of multiple tooth morphotypes, including probable herbivores, indicates that the Driefontein locality preserves a diverse (n>5) archosauromorph assemblage. We interpret this to mean archosauromorphs filled multiple trophic levels within 4 million years of the EPME. This indicates terrestrial ecosystems, at least by dietary groups, may have stabilized from the end-Permian mass extinction in the Early Triassic approximately 5 million years sooner than previously hypothesized.

Authors: Jones, Korin Rex*1, Lisa K Belden1, Myra C Hughey2

Affiliations: 1Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA; 2Department of Biology, Vassar College, Poughkeepsie, NY, USA

Priority effects, or impacts of colonization order, can have a lasting influence on the composition of ecological communities. Externally developing embryos, such as amphibian embryos, experience stochasticity in colonization order by environmental bacteria that ultimately comprise the initial microbiome. To determine if priority effects during embryo colonization impacted bacterial community composition on newly hatched tadpoles, we selectively inoculated the embryos of lab-raised hourglass tree frogs, Dendropsophus ebraccatus, over two days with two bacteria (Acinetobacter sp. and Stenotrophomonas sp.) initially isolated from the skin of wild adult D. ebraccatus in Panama. On day one, each egg received an inoculation of one of the isolates or sterile water. On the second day, eggs received either the same isolate, the alternate isolate, or sterile water. Through 16S rRNA gene amplicon sequencing, we observed shifts in ASV relative abundance within tadpole communities due to priority effects. Being the first inoculum led to increased relative abundance for Acinetobacter, but not for Stenotrophomonas. Our results suggest that the initial microbial source pools that embryos are exposed to shape bacterial communities at later life stages; however, stochasticity in colonization does not impact all bacterial colonists in the same manner.

Authors: Kailing, Macy J.*1, Joseph R. Hoyt1, J. Paul White2, Heather M. Kaarakka2, Jennifer A. Redell2, John E. DePue3, William H. Scullon3, Katy L. Parise4, Jeffrey T. Foster4, A. Marm Kilpatrick5, Kate E. Langwig1

Affiliations: 1Department of Biological Sciences, Virginia Tech; 2Wisconsin Department of Natural Resources, Bureau of Natural Heritage Conservation; 3Michigan Department of Natural Resources; 4Center for Microbial Genetics and Genomics, Northern Arizona University; 5Department of Ecology and Evolutionary Biology, University of California Santa Cruz

Emerging infectious diseases are a key threat to wildlife and understanding disease dynamics within populations is fundamental for the conservation of impacted species. Intersex differences in infection are widely observed across disease systems and may have consequences for host population recovery. We explored sex-biased infections of bat species impacted by an emerging fungal disease, white-nose syndrome, and evaluated disease-associated differences in mortality between sexes and potential effects on population structure. We collected fungal swabs, morphometrics, and environmental data from five species of hibernating bats at 43 sites spanning the eastern and midwestern U.S. to characterize infections and host traits over the course of an annual outbreak. We also used RFID systems at hibernacula and PIT-tagged bats to determine the role of sex-based activity patterns in shaping intersex infection patterns. We found females suffered from more severe infections than male conspecifics when there was a clear sex-bias. In addition, we found females were less likely than males to be recaptured overwinter and accounted for a smaller proportion of populations over time. Notably, female-biased infections were evident by early hibernation, suggesting that sex-based dynamics prior to hibernation may play an important role in shaping WNS outbreaks. Higher fall activity in male bats compared to female bats may enable males to reduce infections relative to female bats. Higher impacts in female bats may have cascading effects on bat populations and extend the consequences of WNS beyond the hibernation season, such as limiting recruitment and increasing the risk of Allee effects.

Authors: Kuchinsky, Sarah C.*1, Jeffrey Marano1, Christa F. Honaker2, Paul B. Siegel2, James Weger-Lucarelli1, and Nisha K. Duggal1

Affiliations: 1Department of Biomedical Sciences and Pathobiology, VA-MD College of Veterinary Medicine; 2Department of Animal and Poultry Sciences, Virginia Tech

Usutu virus (USUVFlavivirus), is an emerging zoonotic virus typically maintained in an enzootic cycle between mosquitos (Culex spp.) and wild birds. USUV is closely related to West Nile virus (WNV) and St. Louis Encephalitis virus (SLEV), both of which are endemic in the United States. Over the last two decades, increased USUV outbreaks have resulted in a rise in human neuroinvasive disease, concurrent with mass mortality events in several avian species across Europe. Yet, the avian species essential for USUV maintenance and the level of viremia (virus in blood) that is required for transmission between host and vector remain elusive. Due to the similarities of USUV, WNV and SLEV, we hypothesize that the minimum infectious threshold for USUV is comparable to these viruses. To investigate the enzootic transmission dynamics of USUV, we sought to establish avian and mosquito infection models. Juvenile chickens from a line selected for low (LAS) antibody production against sheep red blood cells showed susceptibility to USUV, with high viremia levels. Next, we observed a 76% infection rate of American C. quinquefasciatus mosquitos fed an infectious blood meal, indicating that C. quinquefasciatus mosquitos are susceptible to USUV. Thus, to determine the minimum infectious threshold required for transmission, C. quinquefasciatus mosquitos will feed upon our LAS chicken model and USUV infection and transmission rates will be assessed. Discerning the minimum amount of virus necessary for enzootic transmission is critical for identifying maintenance host species, which in turn, can aid in predicting possible spread and emergence of USUV.

Authors: Lofton, Mary E.*1, Dexter W. Howard1, Ryan P. McClure1, Heather L. Wander1, Whitney M. Woelmer1, Alexandria G. Hounshell1, Abigail S.L. Lewis1, and Cayelan C. Carey1

Affiliations: 1Department of Biological Sciences, Virginia Tech

Phytoplankton are essential to lake and reservoir ecosystem function but can also pose water quality concerns by forming harmful blooms. Phytoplankton communities are increasingly affected by a variety of global change stressors, such as warming waters, extreme storms, and nutrient pollution. Disentangling the impacts of these stressors requires an experimental approach. We conducted whole-ecosystem experiments over four summers to assess the response of phytoplankton depth distribution and community structure to thermocline deepening, a disturbance associated with extreme storms. We experimentally deepened the thermocline of a eutrophic reservoir by over a meter for two summers, and then allowed the thermocline to form naturally for two summers. To assess phytoplankton response, we collected weekly depth profiles of phytoplankton biomass, samples for microscope identification of phytoplankton at the maximum biomass depth, and profiles of environmental drivers, including temperature, light, and nutrients. We found that peak phytoplankton biomass was 1.4 m deeper on average in years with deepened thermoclines and that phytoplankton community structure differed in years with deep vs. shallow thermoclines. Shallow biomass peaks were associated with cyanobacteria, desmid, and dinoflagellate taxa, while deep peaks were associated with chlorophyte, cryptophyte, and diatom taxa. Seasonal patterns were similar across years, suggesting that thermocline deepening does not alter expected seasonal succession. Our results inform ecological theory relating phytoplankton distribution to community structure and quantify the strength of phytoplankton response to a global change disturbance.

Authors: Maynard, L. D.*1, M. Y. Bader2, E. Moureau2, D. Salazar3, S. R. Whitehead1

Affiliations: 1Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States; 2Department of Geography, University of Marburg, Deutschhausstraße 10, D-35032 Marburg, Germany; 3Department of Biological Sciences, Florida International University, Miami, FL 33174

Plants allocate their resources based on a myriad of interactions with abiotic and biotic factors. As we are experiencing many climatic changes, including increased temperatures and greenhouse gases (e.g., CO2), we are still uncovering the cascading consequences of climate change on these interactions, particularly in the diversity-rich tropical systems. Here, we address how climate and leaf ontogeny affect plant growth, defense, and herbivory in a neotropical shrub. We used open-top, actively-warmed chambers to experimentally manipulate temperature and CO2 surrounding a neotropical shrub, Piper generalense, in the forest understory at La Selva Biological Station, Costa Rica. We then measured plant growth, foliar chemical defense (total phenolic concentration), and foliar herbivory to detect changes in resource allocation and its effectivityWe found that simultaneous drivers of climate change increased herbivory, as plants in chambers that paired increased CO2 and temperature experienced approximately 3 times more herbivory compared to plants in control chambers. Across all treatments, plants that experienced greater herbivory exhibited less growth in height (an average of 0.9 cm less growth with every 1% increase in average leaf herbivory). Foliar chemical defense was clearly moderated by leaf age, as younger leaves averaged 1.4 times higher phenolic concentrations than mature leaves. Young and more chemically-defended leaves experienced less herbivory (mature leaves had 5.1 times more herbivore damage, and herbivory decreased 1.4% with every 1% increase in total phenolic concentration). However, we found no evidence that the climatic treatments had an effect on plant growth or chemical defense. Plants allocate resources for defense, particularly to younger leaf tissues that aren’t yet physically defended, which helps decrease losses to herbivory. And greater herbivory will ultimately tax the plant, as we observed as less growth in height. The observed increase of herbivory in environments with elevated temperature and CO2 levels may pose an obstacle to plants as climate change exacerbates both, possibly necessitating a shift in plant resource budgeting and allocation. Plants balance a broad spectrum of interactions, and our results emphasize how the roles of climate and ontogeny are inextricably intertwined in species interactions. Understanding the effects of these major players will be a difficult but important task, particularly in the tropics, where chemical- and biodiversity are highest yet sensitivity to a changing climate may be greatest.

Authors: Millican, David M.*1, Ashley. A. Dayer2, and Jeff R. Walters1

Affiliations: 1Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA; 2Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, USA

Surrogate species are common tools for mitigating biodiversity loss, whereby the preservation of one species enables the preservation of entire communities or ecosystems. While most surrogates are selected based on distribution or ecosystem function, the flagship species is unique, selected solely for its ability to act as a marketing symbol for conservation. Effective flagship species garner awareness and financial support, while encouraging the adoption of behavior change to advance conservation objectives. Despite their multipurpose use, flagships have been widely pigeonholed as a tool for generating funding. Consequently, research on flagship selection has fixated on the opinions of the wealthiest stakeholders, who are generally international wildlife viewers from the Global North. Meanwhile, the opinions and experiences of local stakeholders are often omitted from consideration. To better assess the preferences and experiences of local stakeholders, we developed a novel approach to flagship species selection. We conducted semi-structured focus group interviews with conservancy committees throughout Namibia, using emotional prompts to investigate what species traits are associated with positive and negative emotions, and compared our findings to the traits, definitions, and identities of traditional flagship species. Dozens of traits were associated with positive emotions, including many not previously ascribed to flagship species. Meanwhile, traits associated with negative emotions, which are notably lacking from flagship literature, were some of the most prevalent. Our findings indicate that current flagship species selection is myopic, failing to give credence to the experiences of local stakeholders who are ultimately tasked with the conservation of their wildlife.

 

Authors: Moore, C.M.*1, Alexander, T.1, Mims, M.C.1

Affiliations: 1Department of Biological Sciences, Virginia Tech

Biodiversity at its core describes variation among organisms. It is often quantified as species richness, with a high number of co-occurring species designating important ‘hotspots’. However, variation among organisms is not limited to species diversity. Other facets of biodiversity, including life history and phylogenetic diversity, may occur parallel to richness or may be independently distributed spatially. Considering multiple facets may be vital to understand the distribution of biodiversity’s functional and adaptive components, particularly if those facets do not co-occur with richness. We characterized spatial patterns and environmental drivers of species, phylogenetic, and life history diversity of anurans (frogs and toads) in the eastern United States. We measured richness by building species distribution models (SDMs) to estimate the range of 27 anurans of the eastern US using publicly available occurrence and environmental data. We used phylogenetic data and a recently published anuran trait dataset to characterize phylogenetic and life history diversity. Finally, we compared patterns and drivers among facets to quantify areas of redundancy and complementarity. Measuring biodiversity as a multifaceted concept improves our understanding of why anurans occur where they do and can help inform more comprehensive and multidimensional conservation.

Authors: Mouser, J.B.*1, Ciparis, S.1, and Angermeier, P.1,2

Affiliations: 1Department of Fish and Wildlife Conservation, Virginia Tech; 2U.S. Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Virginia Tech

Agricultural best management practices (BMPs) are implemented to protect stream health while continuing agriculture. Stream health goals are often not achieved because the factors controlling BMP efficacy (e.g., landscape conditions, ecological responses, and social factors) are often not considered when installing BMPs. We are using an interdisciplinary approach to assess factors that may influence BMP efficacy. We used the Soil and Water Assessment Tool to model pollutant delivery to streams in southwest VA from 2000–2019. We are also collecting water quality data (E. coli, fecal coliforms, phosphorus, nitrogen, and suspended solids), benthic habitat condition (median pebble size and embeddedness), and benthic macroinvertebrate composition at 31 sites during spring and autumn from 2019–2022. Lastly, we will use surveys to understand landowner persistence in BMP implementation and maintenance after cost-share funding ends. Here, we present preliminary correlations among BMP counts, water quality, benthic habitat, and stream health (Virginia Stream Condition Index; VSCI). BMPs were positively correlated with nitrogen, but uncorrelated with other water quality metrics or VSCI. Benthic habitat was uncorrelated with suspended solids or VSCI. VSCI was negatively correlated with all water quality metrics except fecal coliforms. The relationships between VSCI and water quality parameters were expected; however, we were surprised by the lack of other relationships with BMPs and the positive correlation with nitrogen. Our small sample size may inhibit our ability to detect effects of BMPs given the spatiotemporal variation among sites. Also, BMPs may be too sparse or not in appropriate locations to achieve desired effects.

Authors: O’Brien, C.*1

Affiliations: 1Department of Forest Resources and Environmental Conservation, Virginia Tech

Political polarization is growing in the United States, and environmental issues have been swept up in the rising tide of partisanship. Concomitant with the growth of polarization, there has been increasing use of—and research about—strategic framing in communications. In this context, frames are “interpretive storylines” that highlight aspects of the issues being communicated. They are generally divided into two broad categories: equivalence and emphasis frames. Equivalence frames present logically identical information in different ways, while emphasis frames select different attributes of an issue to spotlight. Frames can impact attitudes, intentions and behaviors across a broad range of contexts, including in the environmental realm. Increasingly, scholars have sought to determine whether the political polarization of attitudes about environmental issues can be overcome through strategic framing. This research seeks to derive lessons from the literature about communicative framing effects on individuals exposed to messages about anthropogenic climate change. Through a systematic literature review, I am exploring relationships among message framing approaches, recipients’ political views, and framing effects. A secondary goal of this research is to examine the prevalence of moral framing in climate change framing literature and the potential role of moral messaging in framing effects, by drawing on Jonathan Haidt’s Moral Foundations Theory. After delving briefly into the background information outlined above, this research power talk will share results from ongoing literature searches and preliminary coding of included articles.

Authors: Pennino, A.*1, McGuire, K.1, Strahm, B.1, Schreiber, M.2, Bailey, S.3, Ross, D.4, Bower, J.4, Duston, S.1, and Benton, J.2

Affiliations: 1Dept. of Forest Resources and Environmental Conservation, Virginia Tech; 2Dept. of Geosciences, Virginia Tech; 3USFS, Northern Research Station, New Hampshire; 4Dept. of Plant and Soil Science, University of Vermont

In small headwater catchments, mass balance approaches for examining elemental fluxes have long been used to interpret watershed nutrient cycling and forest productivity. However, catchment structure (e.g., vegetation, minerology, topography) can vary greatly, and at relatively short distances, therefore flux estimations are often aggregated to a scale that misrepresents what is known about hillslope processes. Our project aims to characterize annual nutrient fluxes within the shallow soil zone along hillslopes at Hubbard Brook Experimental Forest, N.H. using ion exchange resins coupled with hydrological measurements. We hypothesize that annual nutrient fluxes across a watershed are nonuniform due to spatial differences in biogeochemical processes and rates (e.g., mineral weathering, decomposition, leaching). Our hypothesis is supported by distinct spatial patterns in soil and groundwater chemistry that covaries with landscape position. A better understanding of the spatial variability in nutrient fluxes, especially those that are limiting to productivity, is important to quantifying the recovery of base-poor soils and stream water following acid deposition in Northeast forests.

Authors: Pereira, L.A.*1; Castello, L.1 ; Hallerman, E.1

Affiliations: 1Dept. of Fish and Wildlife Conservation, Virginia Tech

Most fish movements in Neotropical river-floodplains coincide with the flood pulse, which is the predictable annual flooding of large rivers. We are studying the migration of two species of catfishes in the Amazon basin, Pseudoplatystoma fasciatum, and P. tigrinum, which are threatened by poorly regulated fishing activities and the construction of hydropower dams that block their migratory movements. Despite these threats, the migrations performed by these catfish have not yet been studied. We, therefore, are addressing the following questions: What is the migration ecology of P. tigrinum and P. fasciatum in the Amazon Basin? Do P. tigrinum and P. fasciatum present homing behavior? To answer these questions, we will characterize the movement ecology of these catfishes by analyzing the trace-chemical composition of Strontium isotopes on their otoliths, i.e., their ear-bones. Otoliths record the chemical signature of the water in which the fish live as they grow and move between waters of different trace chemical compositions. Our analysis of the trace chemical composition of the otoliths will provide the profiles of Strontium isotopes, which will reveal migration patterns along with the life of individuals. These results will be used to inform stakeholders on the migration patterns and critical habitats used by the species to avoid overfishing and to guide the construction of the dams. Thus, this research will produce the knowledge necessary to develop new science-based fisheries policies to sustainably manage and conserve these catfish.

Authors: Plont, S.*1; Riney, J.T.1 ; Hotchkiss, E.R.1

Affiliations: 1Dept. of Biological Sciences, Virginia Tech

Quantifying whole-stream dissolved organic carbon (DOC) metabolism is needed to better integrate inland waters into whole ecosystem carbon budgets. To understand how in-stream DOC metabolism affects DOC removal, export, and terrestrial loading fluxes, we compared DOC removal in two streams estimated using two common methods: (1) bioassays to measure water column DOC uptake velocity; and (2) daily rates of stream metabolism and OC spiraling (i.e., complete OC removal) calculated from fluorescent dissolved organic matter, oxygen, and water level sensor data. We compared how in-stream OC removal estimated from these two methods affected terrestrial OC loading and DOC export using a mass balance model. Mean OC mineralization velocity (0.07 ± 0.04 m/d (±SD)) was greater than mean bioassay DOC uptake velocity (0.01 ± 0.01 m/d). We also observed this discrepancy in DOC removal rates between these two methods in a literature review of nearly 200 estimates. In model simulations, more DOC was removed when using OC mineralization velocity (0.5 to 17.0%) estimates compared to bioassay DOC uptake velocity (0.02 to 4.2%). We highlight how measurement uncertainty of in-stream DOC processing can have confounding effects when estimating terrestrial-aquatic DOC fluxes and removal. By integrating whole-stream metabolism with DOC transport, we can better quantify the role of running waters in the global carbon cycle.

Authors: Rady, J.M.*1; Thomas, R.Q.1

Affiliations: 1Dept. of Forest Resources and Environmental Conservation, Virginia Tech

Forests strongly influence the earth’s climate and the climate mitigation plans set out in the Paris Climate accord rely heavily on both preserving existing forest and expanding forest through reforestation.  Despite this we know relatively little about how the management of forests may need to change under climate change or how planners should use management to achieve climate goals.  In our work we have developed novel tools to simulate many of the major aspects of forest management in one of the leading Earth System Models.  By comparing our computer simulations to forest observations from across the Southeastern United States we have been able to verify that our simulations can reproduce the major events in a managed forest’s lifecycle while simultaneously allowing us to investigate the ability of a demographic vegetation model to simulate ecological competition processes.  These promising results set the stage for future work that will allow us to compare possible forest management alternatives to address global change.

Authors: Smith, D.S.*1 and Wynn-Thompson, T.M.1

Affiliations: 1Dept. of Biological Systems Engineering, Virginia Tech

The impact of root type (e.g. flexible herbaceous roots vs. rigid woody roots) on fluvial streambank erosion is an ongoing debate. Riparian vegetation can change due to a changing climate, human disturbances, and the proliferation of invasive plant species. Understanding how root systems impact the force of flowing water against a streambank is key to informing how vegetation changes may impact geomorphologic processes like streambank erosion. Therefore, the goal of this experiment was to compare the effects of root type on near-bank velocity and boundary shear stress in a laboratory channel. To simulate a vertical streambank with bare soil (no roots), herbaceous roots, and woody roots, three walls were constructed using PVC sheets. Glued sand was used to represent bare soil (SW), while sand + polyester fibers and sand + synthetic plant material represented the flexible rooted wall (FRW) and rigid rooted wall (RRW), respectively. An acoustic doppler profiler was used to measure three-dimensional velocity profiles at multiple flow rates. Though preliminary, results indicate that roots dampen streamwise velocities; the SW had the highest measured velocities, followed by the FRW and then the RRW. Adjacent to the bank surface, shear stress was highest along the FRW and lowest along the RRW, indicating turbulence from the flexible fibers likely increased the hydraulic force on the banks compared to rigid fibers. The higher shear stress produced by the flexible fibers suggests that exposed herbaceous roots along a streambank may increase soil loss due to fluvial erosion compared to exposed woody roots.

Authors: Teemer, S.R.*1 and Hawley, D.M.1

Affiliations: 1Dept. of Biological Sciences, Virginia Tech

Contact rates relevant for pathogen spread are shaped by behavior, and in turn, behaviors of susceptible and infected hosts are influenced by temperature. House finches (Haemorhous mexicanus), a songbird species, can become infected with the bacterial pathogen Mycoplasma gallisepticum (MG) through direct contact with infected conspecifics or indirect contact via shared use of bird feeders. MG causes the disease mycoplasmal conjunctivitis and outbreaks primarily occur in fall and winter. At cold temperatures, house finches rely on feeders to meet increased energy demands, which may increase contact rates between infected and uninfected birds. However, the role of ambient temperature in driving behaviors relevant to transmission has not been studied. To determine how temperature influences behaviors and contact rates important for MG spread, we manipulated ambient temperatures (thermoneutral or subthermoneutral) for pair-housed birds and quantified feeding behaviors. We measured contact rates using a fluorescent transferrable powder applied around the conjunctiva of one “index” bird per pair and quantified the amount of powder directly or indirectly transferred to cagemates. To account for effects of sickness behaviors on contact rates, half of the index birds in each temperature group were given lipopolysaccharide injections to induce sickness behaviors similar to those in birds infected with MG. Because behavior and contact rates are integral in determining likelihood of pathogen spread, it is important to understand factors that affect both components. Thus, this experiment can provide insight into the role of the abiotic environment on transmission in this system and other infectious diseases more broadly.

Authors: VanDiest, I.J.*1, Lane, S.J.1, Sewall, K.B.1

Affiliations: 1Dept. of Biological Sciences, Virginia Tech

Urbanization presents new challenges to organisms that persist in modified habitats. Urban environments can havereduced biodiversity, altered nutrient availability, and thus, species that persist in urban habitats may have access to less nutritious food or less food overall. Previous work has found that arthropod communities upon which many songbirds rely during breeding are of lower trophic levels in urban environments. A study in crows found that urban nestlings had lower plasma protein and calcium relative to rural nestlings. To determine how urbanization might impact food availability and nutritional quality for song sparrows we completed arthropod surveys 5 times during the breeding season and measured circulating whole protein and calcium levels from 64 urban and 25 rural nestlings across 3 rural and 3 urban sites. We found that our urban study sites had lower arthropod biomass, lower ratios of nutritionally rich orders (e.g. Aranae) and fewer arthropods overall compared to rural sites. Despite differences in arthropod communities we did not find differences in nestling plasma protein across habitats. Rather, protein increased with age (p=0.0176). Calcium was higher in urban areas (p=0.0082), but there was an inverse relationship between age and circulating calcium in urban habitats (p=0.0123) such that older nestlings had less calcium. These data suggest that urban habitats, though harboring fewer arthropods, may not be nutritionally limiting and that nestlings receive equal and presumably adequate nutrition in both habitats. Future studies will compare diet by measuring what parents are feeding young, and will consider other measures of nestling nutrition.

Authors: Wynd, Brenen M.*1, Josef C. Uyeda2, and Sterling J. Nesbitt1

Affiliations: 1Dept. of Geosciences, Virginia Tech; 2Dept. of Biological Sciences, Virginia Tech

Allometry, patterns of relative change in body parts, has been a standard to reconstructing patterns of growth within and across animals. Recording allometry through measurements is one of the few methods available to reconstruct growth in fossils. However, many fossil specimens are deformed during fossilization. Deformation can influence recovered allometric patterns by outlier effects, shifting results away from the original biology. Previous studies have removed distorted measurements from analyses; however, this removes variation and limits the number of samples. The issue lies in the method, not the specimens. Linear regression is sensitive to outliers, as opposed to a generalized linear mixed model (GLMM) which can code specimens as distorted. To test the efficacy of a GLMM, we performed a simulation based on measurements of the cynodont, Exaeretodon argentinus. To estimate the effects of distortion, we added variation to half of our simulated sample using a binomial distribution. We tested three models, with 1,000 repetitions each: linear regression without added variation, linear regression with added variation, and GLMM with added variation. We found that a linear regression of 10 non-deformed samples performed nearly equivalent to a GLMM of 15 samples including added variation. To validate these findings, we performed a nonparametric bootstrap analysis on two datasets. Results of the bootstrap analysis support our simulations such that the GLMM is better able to reconstruct patterns of allometry in samples with deformation. Our study suggests that a GLMM can better reconstruct patterns of allometry over a linear regression, given fossil datasets.

Frog Jumping

Due to  the COVID-19 pandemic and in alignment with Virginia Tech’s large event cancellation strategy, we regret that the 5th Annual IGC Graduate Research Symposium was cancelled in 2020.

 

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April 3, 2020

Interfaces of Global Change Graduate Research Symposium

 

Graduate Life Center, Multipurpose Room

 

The fifth annual Interfaces of Global Change (IGC) Graduate Research Symposium will be a great opportunity for IGC Fellows to share their research with the entire global change community at Virginia Tech. The symposium was scheduled for Friday, April 3rd, to provide a forum for students and faculty to interact and explore connections between labs across campus.

GCC faculty affiliates and current and prospective IGC graduate students are invited to attend the annual symposium.

IGC fellows, please visit the Presentation & Abstract information page for more information.

Keynote Lecture by Patterson Clark

Photo credit: NPR

Patterson Clark will deliver the keynote address as part of the 7th Annual Interfaces of Global Change Graduate Research Symposium. Clark is senior graphics editor for POLITICO Pro. He previously worked for The Washington Post as science graphics editor and also wrote and illustrated the natural history column Urban Jungle. At the Miami Herald, he was on the team of journalists honored with the 1993 Pulitzer Prize for Public Service for their coverage of Hurricane Andrew and its aftermath. Before that, Patterson was an op-ed illustrator and news artist for his home-state newspaper, the Arkansas Gazette.

Clark has harvested D.C.’s exotic invasive vegetation for over twenty years, exploring its potential for use as art, food, fuel and fiber. More information about his artistic work utilizing invasive plants can be found on his website at https://alienweeds.com/index.html.

8:00 – 8:45 am  –  Poster set up; refreshments available

8:55 am  –  Welcome

9:00 – 10:25 am – Oral Presentations Session 1

10:25 – 11:40 am – Poster Session Group 1

11:40 am – 12:55 pm – Lunch

1:00 – 2:15 pm – Keynote Lecture by Patterson Clark

2:15 – 2:30 pm – Break

2:30 – 3:45 pm – Oral Presentations Session 2

3:45 – 5:00 pm – Poster Session Group 2

5:00 – 6:00 pm – Reception; Platform Awards Announced

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4th Annual

Interfaces of Global Change Graduate Research Symposium

April 25, 2019
Fralin Hall

The Fourth Annual Interfaces of Global Change (IGC) Graduate Research Symposium was held on April 25, 2019 in Fralin Hall. The gathering provides a forum for students and faculty to interact and explore connections between labs across campus. The day included 12 oral presentations and a poster session by 24 students.

The symposium highlighted the latest research from the program’s graduate student fellows, whose collective work addresses critical global changes impacting the environment and society. This includes problems surrounding climate change, pollution, invasive species, disease, and habitat loss.

Platform awards for Best Presentation were selected for the top three oral presentations. This year’s winners were:

First Place Angie Estrada, “Amphibian translocations: skin microbiome, body condition and disease status”

Second Place Ernie Osburn, “Forest disturbance alters soil microbial community structure and function in Appalachian ecosystems”

Third Place Stephen DeVilbiss, “Effects of freshwater salinization and associated base cations on fecal indicator persistence and bacterial community structure”

Kudos to all the student participants!  Your work is truly inspiring, important and impactful to the Virginia Tech community and beyond.  Thank you to the GCC Faculty and other researchers on campus who came out to show their support for the IGC Fellows!

See more photos from the Symposium on FLICKER

Detailed AGENDA PDF

8:00 a.m.         Poster setup, coffee & refreshments; Fralin Hall Atrium

8:55 a.m.         Welcome; Fralin Auditorium

9:00 a.m.         Oral Presentations, Session 1; Fralin Auditorium

10:00 a.m.       Break and poster viewing

10:30 a.m.       Oral Presentations, Session 2; Fralin Auditorium

11:45 a.m.        Lunch and poster viewing; Fralin Atrium

1:00 p.m.         Oral Presentations, Session 3; Fralin Auditorium

1:45 p.m.         Poster Reception (students by posters); Fralin Atrium

3:00 p.m.         Platform Award Announcements; Fralin Atrium

3:15 p.m.         Symposium Adjourns

All IGC fellows who are in their 2nd year of PhD study or beyond are encouraged to present their work at the symposium in the form of a poster or talk. The number of oral presentations will be limited to approximately 12, and the number of posters limited to approximately 28. Senior IGC Fellows in their 3rd, 4th or 5th year of study are strongly encouraged to select to give a talk, especially if they have not done so in past symposia. Awards will be given for best talks.

FORMAT

Each abstract should contain:

  1. Title
  2. Authors and Affiliations (e.g., Department and University), presenting author denoted by an asterisk.
  3. An abstract not to exceed 250 words in length

Format example:

Hopkins, W.A.*1, Dude, T.H.E. 1,2, and Sobchak, W. 1
1 Dept. of Fish and Wildlife Conservation, Virginia Tech; 2 Dept. of Interior Room Design, University of Abides

POSTERS: maximum poster size is 40″ x 60″.  An easel and backboard will be provided.

Platform Session 1   9:00 – 10:00 a.m.
Session Chair: Nicole Ward

 

Switchgrass as a Climate Change Mitigation Tool in Central Virginia

Authors: Benjamin J. Ahlswede* 1, Tom L. O’Halloran 2, R. Quinn Thomas 3

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. Department of Forestry and Environmental Conservation, Clemson University, Clemson, South Carolina 3. Department of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Switchgrass (Panicum virgatum) has emerged as an ideal bioenergy crop due to its ease of maintenance, high productivity, and potential for climate change mitigation. However, only a handful of studies have examined the year-round carbon dynamics of a switchgrass field, and these have typically been conducted with newly established fields, or on experimental plots with active management plans. Here we present intra- and inter-annual dynamics of carbon dioxide exchange from three growing seasons of eddy covariance observations above a mature and minimally managed switchgrass field in central Virginia. This field was a net-source of carbon to the atmosphere over the entire observation period. However, the field can switch from a sink to a source depending on weather conditions and harvest timing. This observation period includes the wettest year ever recorded for this region. This increase in precipitation enhanced respiration, but also reduced productivity leading to a marginally small source of carbon at the end of the observation year. Previous work has shown switchgrass to be a sink of carbon from the atmosphere. In order to evaluate the effectiveness of biofuel switchgrass as a climate change mitigation strategy, all potential conditions and management scenarios need to be considered.

 

Analysis of antibiotic resistance genes and present microbial communities in agricultural soils amended with various manure-derived amendments

Authors: Wind L.* 1, Krometis L.-A. 1, Hession W.C. 1, Pruden A. 2

Affiliations: 1. Dept. of Biological Systems Engineering, Virginia Tech 2. Dept. of Civil and Environmental Engineering, Virginia Tech

Increasing evidence links the widespread use of antibiotics in livestock production to the transfer of bacteria carrying antibiotic resistance genes (ARGs) to the broader environment. The relative impacts of agricultural practices, climatological factors, and native soil microbiota on the local resistome is complex. The overall goal of the present study is to employ molecular “indicator”-and next-generation sequencing-based techniques to characterize the impacts of various manure-derived soil amendments on ARG profiles in agricultural soils. Observations of multiple resistance markers in tandem allows for a more holistic characterization of present soil microbial community composition and the potential impacts from common agricultural practices. In brief, fifteen 9-m2 field plots were planted with lettuce and fertilized to test the effects of fertilizer type (inorganic, compost, raw manure) on the soil resistome. Soil samples were collected over 120 days, and quantitative polymerase chain reaction (qPCR), 16S rRNA gene amplicon sequencing, and shot-gun metagenomic sequencing were used to analyze the present soil microbial communities. ARGs (sul1, tet(W), erm(B)) and the class 1 integrase gene (intI1) were monitored as “indicators” of anthropogenic sources of antibiotic resistance. Raw dairy manure amended soils yielded high relative sul1 and tet(W) gene copies on Day 0, correlating with an observed spike in associated ARBs. Network analysis of the soil microbiome identified rpoB2 as the most abundant plasmid-associated gene, which may prove to be useful targets for monitoring in agricultural scenarios. Analysis of the microbial community composition and broader metagenome is underway, with the goal of comprehensively comparing effects of the amendments on the soil taxonomic and functional profiles. These findings will provide insight on how ARGs potentially spread throughout agricultural soils by linking known microbial community presence and metagenomic profiles.

 

Forest disturbance alters soil microbial community structure and function in Appalachian ecosystems

Authors: Ernest D Osburn* 1, Jennifer D Knoepp 2, John E Barrett 1

Affiliations: 1. Dept. of Biological Sciences, Virginia Tech 2. USDA Forest Service, Coweeta Hydrologic Laboratory, Otto, NC

In Appalachian ecosystems, human disturbances such as forest clearcutting have been shown to alter rates of soil ecosystem processes such as carbon (C) and nitrogen (N) cycling. However, effects of forest disturbance on soil microbial communities and relationships between altered microbial communities and ecosystem processes have not been examined. To address these questions, we selected four historically disturbed watersheds and four undisturbed reference watersheds at the Coweeta Hydrologic Lab in the mountains of North Carolina. In each watershed, we established six plots and sampled soils from each plot. We then determined concentrations of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), ammonium (NH4), and nitrate (NO3) in all soil samples. We also determined rates of microbial C and N mineralization in laboratory incubation experiments. Finally, we isolated DNA from soil samples and assessed bacterial vs fungal dominance via qPCR and microbial community structure via sequencing of the 16s rRNA gene. Our results show reduced DOC concentrations and elevated inorganic N (NH4, NO3) concentrations in disturbed soils. Additionally, we found that microbial communities in disturbed soils displayed higher rates of C and N mineralization relative to reference soils. Finally, we found that disturbed soils had increased dominance of bacteria over fungi and that disturbed soil bacterial communities were distinct from reference soil bacterial communities. We suggest that higher rates of C and N cycling following forest disturbance may be attributed to increased abundance of copiotrophic microbial taxa (i.e. increased bacterial dominance) characterized by inefficient use of soil C and N resources.

 

Using Social Science to Understand the Relationship between Recreationists and State Wildlife Agencies

Authors: Grooms, B. P.* 1, Dayer, A. A. 1, and Peele, A. 2

Affiliations: 1. Dept. of Fish and Wildlife Conservation, Virginia Tech; 2 Conservation Management Institute, Blacksburg, VA

State wildlife agencies benefit from wildlife recreationists’ financial contributions and support of agency conservation efforts. Yet, agencies currently face a changing stakeholder base, including declines in traditional sources of support (i.e., hunters and anglers), and increased interest for involvement from other stakeholders (i.e., birders and wildlife viewers). As such, research into recreationists’ perceptions of agencies can help agencies better respond to them and engage them in conservation. For this reason, we investigated recreationists’ trust and the perceptions of distributive justice of provided services of the Virginia Department of Game and Inland Fisheries (DGIF). We conducted two focus groups with each of four wildlife recreation groups (birders, wildlife viewers, hunters, and anglers), involving 83 recreationists. We found birders’, wildlife viewers’, and anglers’ trust was rooted in positive, personal interactions with DGIF employees, and on positive perceptions of past effectiveness by the agency. Birders and wildlife viewers were generally less trusting of DGIF than hunters and anglers. Additionally, we found all recreation groups felt DGIF did not equally distribute services. These feelings were more common in birders and wildlife viewers who felt their services were sometimes secondary to those for hunters and anglers. Results suggest DGIF focus on building trust with birders and viewers by forming positive, personal interactions. DGIF could also expand the availability of benefits to their broader stakeholder base to address concerns of equity. Doing so may help DGIF engage with new stakeholders, foster support in agency programs, and facilitate public participation in agency conservation efforts.

Platform Session 2   10:30 – 11:45 a.m.
Session Chair: Brenen Wynd

 

Ecological recovery following the end-Permian Mass Extinction recorded in Middle Triassic tooth assemblage

Authors: Hoffman, D.K.* 1, Edwards, H. 2, Barrett, P.M. 3, Nesbitt, S.J. 1

Affiliations: 1. Dept. of Geosciences, Virginia Tech, Blacksburg, VA  2. Dept. of Geology, University of Georgia, Athens, GA  3. Earth Sciences, Natural History Museum, London, UK

Mass extinctions provide a biological “reset” often linked to subsequent biological radiations, which are marked by species diversification and ecological specializations. However, the relative timing of species and ecological diversification is unclear. The radiation of archosauromorphs (birds, crocodylians, and their extinct relatives) following the end-Permian Mass Extinction provides a test for disentangling radiations. One measure of ecology in the fossil record is teeth through diet, although tooth assemblages immediately following the extinction are rare, limiting their utilization during this critical time. However, recent fieldwork in the Middle Triassic of Tanzania has revealed a tooth assemblage that partially fills this gap. To reconstruct the species composition of the assemblage we used in situ teeth of known taxonomic assignment and additional 31 isolated teeth of unknown species affiliation. Continuous measurements (observations = 71) produced a linear relationship of tooth height predicting tooth base ratio (=base length/base width). Using this relationship, we generated a morphospace in which the majority of isolated teeth fell within a zone of overlap shared by several species. The discrete method (observations = 67) of eleven binary characters removed the potential influence of size and reduces overlap among species. The majority of the isolated teeth fall within an overlap of two taxa morphospace. The significant overlap of tooth shape among species and overall similarities indicate that ecological diversification lagged behind species diversification in archosauromorphs. Though only a single locality, the methods used herein offer a promising lens to reconstructing ecological radiations and are readily transferable across Earth history.

 

Variation in seed germination traits of an invasive grass is explained by climate

Authors: Rebecca Fletcher* 1, Kayla Varnon 1, Jacob Barney 1

Affiliations: 1. School of Plant and Environmental Science, Virginia Tech

Seed germination is an essential life history event for most flowering plants, because it leads to subsequent generations and dispersal to new habitats. Because germination is one of the earliest phenotypes expressed by plants, the timing of seed germination in response to environmental cues can have important implications for seedling survival and lifetime fitness, as well as range dynamics. Variation in climate conditions throughout a species’ range, especially invasive species which often span large geographic ranges, may promote adaptation of germination in response environmental cues such that germination timing is optimized in order to maximize fitness. We investigated germination in response to temperature using the invasive grass Sorghum halepense (Johnsongrass). Previous work with Johnsongrass has provided strong evidence of genetic and phenotypic differentiation associated with climate as populations have expanded increasingly northward. We collected seeds from 10 populations of Johnsongrass throughout its North American range and exposed them to temperatures ranging from 11˚C to 48˚C. We estimated the minimum (Tmin), maximum (Tmax), and optimum (Topt) temperature of germination. We found substantial differences between populations for all three temperature parameters. All three germination traits had a positive relationship with mean annual temperature suggesting that there has been divergence in germination response of Johnsongrass populations to local climate conditions. It is possible that adaptation of germination in response to environmental cues has been a contributing force in the range expansion of Johnsongrass.

 

Effects of freshwater salinization and associated base cations on fecal indicator persistence and bacterial community structure

Authors: DeVilbiss, S.E.* 1, Badgley, B.D. 1, Steele, M.K. 1

Affiliations: 1. School of Plant and Environmental Sciences; Virginia Tech

Anthropogenic activities including agriculture, urbanization, and surface mining have been increasing total salinity and associated base cations in surface waters worldwide. It is well documented that large increases in salinity (i.e. freshwater to marine) significantly decrease the persistence of the fecal indicator E. coli and alter aquatic bacterial community structure. However, linkages between small increases in salt concentrations within the freshwater range (≤ 1,500 µS/cm) and bacterial surface water quality have yet to be explored. Further, effects of different types of salts and their associated base cations (Ca, Mg, K) on aquatic bacterial ecology remain unknown. Through a series of controlled mesocosm studies, we demonstrate that freshwater salinization increases the persistence of E. coli at very low salt concentrations (<200 µS/cm), which is opposite the trend observed over broad salinity gradients. Specific base cations also had a significant effect with Mg increasing E. coli persistence by up to 40%. Additionally, different base cations had significant, differential effects on freshwater bacterial community structure. These results indicate that low levels of freshwater salinization may exacerbate bacterial impairments and alter bacterially mediated ecosystem functions. Effects may be magnified in watersheds with high Mg concentrations. Implications include: 1) reducing salt loads to surface waters may reduce bacterial impairments and 2) a more nuanced approach to salinity research and management that considers salt sources and types rather than total salinity may be required to preserve surface water quality.

 

Forest Management in Space and Time, When it Matters and When it Doesn’t

Authors: Rady, J.M.* 1, Ahlswede, B.J. 1, Thomas, R.Q. 1

Affiliations: 1. Forest Resources and Environmental Conservation, Virginia Tech

Managed forests differ from unmanaged “natural” forests in ways that are relevant to climate. By manipulating forests to maximize timber production land surface properties and carbon fluxes are altered in time and space. Despite the potential implications for climate, the Earth System Models (ESMs) used to examine the climate influences of forests and land-use/land-management at global scales capture few aspects of forest management. To explore the potential importance of forest management to climate we conducted experiments using the Community Land Model (CLM) Version 5.0 within the Community Earth System Model. We changed the CLM’s assumptions about how wood is harvested in order to simulate protected areas (e.g. national parks, conservation lands) and clear-cut harvest rotations and examined the impact on forest carbons stocks, structure, and surface energy fluxes. We found that removing wood from a reduced area of forest caused limited changes to model output. On the other hand, we found that harvesting wood in clear-cut rotations caused notable changes in carbon stocks and surface energy fluxes. This suggests that the uniform approach to wood harvest in the CLM may lead to overestimation of forest biomass and carbon sequestration. Furthermore forests with rotational harvest show a different response to changing climate in the twenty first century. This work is a step towards better understanding how human manipulation of forests influences climate and allows the further exploration of how altering these practices might be used to mitigate climate change.

 

Amphibian translocations: skin microbiome, body condition and disease status

Authors: Angie Estrada* 1, Daniel Medina 1, Brian Gratwicke 2, Roberto Ibáñez 3, Lisa K. Belden 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech 2. Smithsonian’s National Zoo & Conservation Biology Institute 3. Smithsonian Tropical Research Institute, Panama

Beneficial skin bacteria can protect amphibians against Batrachochytrium dendrobatidis (Bd), a deadly pathogenic fungus that is one of the largest threats to amphibians worldwide. For many species, long-term captive breeding programs have prevented extinction; however, captive management is known to modify the amphibian skin microbiome. In Panamá, threatened amphibian species survive in captive breeding facilities, but it is unknown how skin microbiome change once captive-bred individuals are re-exposed to natural habitats. Thus, to inform the development of beneficial bacteria-based treatments and future captive-to-wild translocation efforts, we aimed to assess the changes that occur in the bacterial communities of Atelopus limosus, a critically-endangered species, following soft-release to a site where the species historically thrived. We aimed to investigate how the initial skin bacterial community influences: 1) bacterial community structure and composition after release, 2) host condition and 3) Bd infection status. Frogs were housed in mesocosms to be monitored and sampled through time and next-generation sequencing technology was used to identify bacterial taxa. We found significant variation in skin microbiome once exposure to natural conditions occurred. Moreover, after only two weeks, reintroduced and wild individuals had more similar skin microbiomes. Body condition decreased and a small proportion of frogs got infected with Bd but mortalities were not associated with weight loss nor disease status. These preliminary findings suggest that skin-associated microbiomes of captive-bred amphibians can be restored, but future research needs to address whether these changes in bacterial structure ultimately result in higher survival and Bd protection of captive-bred amphibians.

Platform Session 3   1:00 – 1:45 p.m.
Session Chair: Sydney Hope

 

Ecological recovery following the end-Permian Mass Extinction recorded in Middle Triassic tooth assemblage

Authors: Zach Martin* 1, and Paul Angermeier 1,2

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Tech 2. U.S. Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Spawning behaviors represent an understudied bottleneck to fitness in stream fishes and play a mechanistic role in how substrate embeddedness leads to local extirpations. For example, embeddedness may limit reproductive success of cavity-nesters by reducing optimal nesting space underneath rocks. We designed two laboratory experiments, using cavity-nesting fantail darters, to test effects of embeddedness on oviposition. We placed spawning pairs in Living Stream tanks for five-day trials with sand as a bottom substrate and 6-in x 6-in ceramic tiles as potential nest substrates. We presented fish with four “embeddedness” treatments vary in degree of tile burial and availability of a benthic cavity. One experiment presented spawning pairs (n=120; 30 per treatment) with one tile and one treatment; oviposition (0/1) and clutch size were responses. The second experiment (n=90) presented spawners with four tiles (one per treatment); nest-rock choice, oviposition, and clutch size were responses. Spawners from both experiments oviposited on tiles of all but the most embedded treatment, and most commonly on tiles lying flat on sand with a cavity provided. Four spawning pairs excavated cavities and oviposited on moderately embedded tiles. Spawners also oviposited on tank walls; in experiment one, these instances coincided with the two most embedded treatments. Our observations suggest this tolerant darter has limited ability to spawn in habitats smothered by fine sediments. The nonlinear, negative relationship between embeddedness and reproductive success we found conflicts with traditional assumptions made by researchers, and ultimately managers, about the role of sediment pollution in reproductive failure and extirpations.

 

Can agricultural practices mitigate climate change? The impact of ‘no-till’ practices on soil carbon using an Earth system model

Authors: Michael W. Graham* 1, R. Quinn Thomas 2, Danica L. Lombardozzi 3, Megan E. O’Rourke 4

Affiliations: 1. Geospatial and Environmental Analysis Program, Virginia Tech 2. Dept. of Forest Resources and Environmental Conservation, Virginia Tech 3. National Center for Atmospheric Research, Boulder, CO 4. School of Plant and Environmental Sciences, Virginia Tech

Soil tillage is a ubiquitous management practice on croplands globally, and is thought to have historical impacts on climate through accelerated decomposition of soil C and increased CO2 emissions on agricultural land. Conservation tillage (e.g. ‘no-till’) has been proposed as a mechanism for mitigating climate change through increased soil C storage on croplands. The magnitude of these effects remains unknown and likely varies through space and time. Earth system models (ESMs) are useful tools to understand the spatial and temporal impacts of tillage, though few studies have examined different soil tillage practices in ESMs. ESMs tend to underestimate historical C fluxes and aggregate biogeochemical impacts of land management practices on climate relative to empirical records. Here we use the Community Land Model (CLM), the land component of the Community Earth System Model, to assess 1) biogeochemical effects of soil tillage by testing the global sensitivity of soil C stocks in CLM to intensive conventional tillage practices of different intensities over the historical time period (1850-2014), and 2) climate change mitigation potential of conservation tillage practices by evaluating the sensitivity of CLM soil C stocks to lower levels of tillage intensity associated with conservation tillage practices for a future climate scenario (2014-2100). Results indicate that increasing tillage intensity increases soil C decomposition rates; total losses in soil C due to intensive tillage practices are 17 Pg C for the historical time period, or 11% of estimated historical C emissions from land use change. Larger differences in tillage intensity and lower decomposition rates for conservation tillage relative to intensive tillage results in greater soil C storage over the future climate scenario. Historical losses are tightly coupled temporally and spatially with land use change to crops and losses due to tillage increase over time with cropland expansion. These results show that carbon impacts of tillage depend on parameters governing the decomposition rates when tillage is applied, as lower tillage intensities have smaller soil carbon impacts.

 

Relative importance of top-down versus bottom-up control of phytoplankton vertical distribution in north temperate lakes

Authors: Mary E. Lofton* 1, Taylor H. Leach 3, Beatrix E. Beisner 2, and Cayelan C. Carey 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA 2. Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, USA 3. Department of Biological Sciences, University of Québec at Montréal, Montréal, QC, Canada

Many freshwater and marine ecosystems exhibit deep chlorophyll maxima, in which phytoplankton biomass is most concentrated below the water surface. In lakes, these deep layers of biomass are hypothesized to be either controlled by nutrient and light concentrations or zooplankton grazing pressure in surface waters. However, few studies have explicitly compared the importance of both bottom-up and top-down forces on vertical distributions of different phytoplankton groups. We collected fluorescence-based depth profiles of four phytoplankton spectral groups and a suite of environmental data (zooplankton, total phosphorus, temperature, and water color) from 56 dimictic lakes in Québec, Canada at the height of summer stratification in 2004 and 2005. We calculated several phytoplankton vertical distribution metrics for each spectral group and used regression trees to assess the most important driver of phytoplankton vertical distributions at each time point. We found that while bottom-up drivers control most characteristics of phytoplankton vertical distributions, zooplankton abundance is the most important driver of the depth of chlorophyll maximum. Furthermore, vertical distributions of various phytoplankton spectral groups respond to different drivers, which may be related to the life history of these taxa. For example, zooplankton emerged as the most important driver for two of three vertical distribution metrics for brown algae, a spectral group containing taxa that are known to be particularly nutritious and therefore a preferred food source for zooplankton. Our results provide empirical evidence to support both top-down and bottom-up control of deep chlorophyll maxima in lakes during the stratified period.

* denotes presenting author

Adaptive radiation in the multidimensional phenotype

Authors: Brooke L. Bodensteiner* 1 and Martha M. Muñoz 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech

Adaptive radiations are considered a special case of evolutionary diversification in which a clade displays extraordinary ecological and phenotypic diversity. A common feature that unites studies of adaptive radiation is that the ecology-phenotype connection has been almost exclusively described in terms of morphology. For example, the adaptive radiation of Caribbean anoles is known for the evolution of distinct ecomorphs,, which are so-named based on the tight association between structural habitat use and morphological traits in these lizards. Despite all the of the disproportionate attention that morphological traits have received, it has also been well-recognized that physiological evolution, along a thermal gradient, is also a key aspect of the adaptive radiation of anoles. Here we test how morphological and physiological disparity compare by examining the morphology and thermal physiology of Hispaniolan anoles. Elucidating that physiological patterns of evolution do not mirror morphological patterns of evolutionary divergence. We propose that thermoregulatory behavior may be guiding these macroevolutionary patterns revealed by this study.

 

The invasive tree-of-heaven’s (Ailanthus altissima) relationship with understory and seedbank plant species

Authors: Brooks, R.K.* 1, Barney, J. 1, Salom S. 2, Baudoin, A. 1

Affiliations: 1. School of Plant and Environmental Sciences, Virginia Tech 2. Department of Entomology, Virginia Tech

Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae), commonly known as the tree-of-heaven, was introduced to Pennsylvania in 1784 from China. Since then, this tree has spread to over 40 states. In Virginia, it is found ubiquitously in urban areas, along road ways, bordering agricultural lands, and in forests. Though Ailanthus has been shown to be associated with decreased levels of above-ground plant species richness and native species diversity in a few studies, this relationship has not been consistently found. Additionally, its impact to the seedbank (viable seeds or vegetative propagules present in the soil) has yet to be studied. To further understand this invasive tree’s impact, ten paired invaded-uninvaded sites were identified in Montgomery, Giles, and Pulaski Counties. The established canopy and understory for each plot was measured, and soil samples were collected and grown out for 5.5 months in a greenhouse. All germinating plants were identified to the highest taxonomic level possible. In total, 96 species of understory plants and 77 species of seedbank germinants were identified. Furthermore, stand size and age of each invaded plot was estimated, ranging from 2-53 years and 3-4,200m2 respectively. A preliminary analysis of the relationship between Ailanthus presence, the understory, and the seedbank is presented, followed by a discussion of its future implications.

 

Fish assemblage impacts of reef fisheries in tropical Brazil

Authors: Carvalho, F.M. 1, Castello, L.* 1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Tech

Tropical marine environments are threatened by high fishing pressure and use of nonselective fishing gears that cause the decline and even ecological extirpation of key fish populations. Such declines have the potential to change species community composition, and associated energy fluxes for whole marine communities. The goal of this research is to identify fishing gears that harm the ecosystem because they catch disproportionate amounts of non-target species and/or undersized individuals. The project will take place in the “Marine Protected Area Coast of Corals”, an area where over 100 species are regularly harvested. This includes the iconic and endangered Atlantic goliath grouper (Epinephelus itajara), which is often caught as bycatch. The data collection involves interviews with local fishers during the moment of the landing in fishing ports. An effort will be made to record the total catch per species, besides the size of each individual caught. The specific characteristics of the gears used (e.g. traps, beach seines, bottom trawlers, hand lines, spears and gill nets) will also be registered such as the length and mesh sizes of nets, size and number of hooks, etc. By identifying “harmful” gears, this project will help reverse current degradation trends by providing recommendations of gear restrictions. By evaluating our results in the context of ongoing fishing practices, our research will have direct application to fisheries management and ecosystem conservation

 

Predictability in the Evolution of Tetrodotoxin Resistance in Reptiles

Authors: Gendreau, K.L.* 1, Hornsby, A.D.1, and McGlothlin, J.W.1

Affiliations: 1. Department of Biological Sciences, Virginia Tech

Predicting the presence or magnitude of traits based on genome sequences is a major challenge in modern evolutionary research, and improving our understanding of the relationships between genotypes and phenotypes can help us to more accurately forecast how populations will respond to changing environmental conditions. Cases of convergent evolution, in which the same trait has evolved independently in different lineages, are particularly useful in addressing this challenge. We used comparative genomics to investigate the molecular basis of tetrodotoxin (TTX) resistance, which has evolved independently in multiple snake species that consume TTX-bearing amphibians. We found evidence for a predictable, stepwise pattern of nucleotide substitution occurring in the genes targeted by TTX (members of the voltage-gated sodium channel gene family). We also found evidence for positive selection within the TTX-binding regions of these genes. In addition to selective pressure, changes in genetic structure and increased mutation rates may have contributed to the evolution of resistance in select colubrid snake species. These results shed light on the molecular underpinnings of complex trait evolution, and provide a basis to search for similar patterns in other taxa that encounter TTX, such as the toxic amphibians themselves.

 

Microbiome mediated plant-pollinator interactions in non-agricultural systems

Authors: Ariel Heminger* 1 and David C. Haak 1

Affiliations: 1. School of Plant and Environmental Sciences, Virginia Tech

Plant-pollinator interactions are one of the most widely recognized coevolutionary relationships. Darwin attributed the rapid diversification of flowering plants to this close association with their insect partners and these partners often depend on plants for pollen and nectar as a food source. Woven into this relationship are microorganisms that form close relationships with their hosts forming the microbiome. The microbiome is intricately associated with the organismal health through processes such as nutrient acquisition and disease suppression. This suggests that flowers and their pollinators could have reciprocal influences on their associated microbes that have been shaped over evolutionary time. Few studies have examined the impact of this reciprocal interaction on microbial community structure, eco-evolutionary dynamics, or plant health. This study aims to fill this gap through characterizing the floral and pollinator microbiome across several natural populations of Solanum carolinense and Solanum dulcamara (an introduced species) and their pollinator Bombus spp. Eighty samples from the first year of the study were sequenced which resulted in 1475 unique OTUs before filtering. Preliminary results from these samples indicate that the floral microbiome changes throughout the developmental stage of the flower and that OTUs were differentially abundant on caged versus uncaged flowers. This suggests that pollinators introduce particular microbes to flowers during their visits, therein shifting the floral microbiome. Future studies aim to determine the similarities between the pollinator microbiome (gut and pollen baskets) and the flowers they visit. These studies will contribute to the body of knowledge on plant-pollinator interactions at the microbial level.

 

The influence of extra-pair activity on the cloacal microbiome of a free-living bird

Authors: Jessica Hernandez* 1, Lisa Belden 1, Ignacio Moore 1

Affiliations: 1. Department of Biological Sciences Virginia Tech

Socially monogamous females that engage in extra-pair activity (e.g., solicitations, copulations, fertilizations) face potential fitness trade-offs including, but not limited to, good genes and genetic diversity in offspring, but also loss of paternal care and increased harassment by their social partner. Sexually transmitted (pathogenic) microbes have been suggested to be a cost of extra-pair activity for female birds for nearly five decades, but this hypothesis has not yet been adequately tested. To determine how extra-pair activity is related to the composition of the cloacal microbiome, we performed an observational study on free-living female tree swallows (Tachycineta bicolor) during the breeding season in southwestern Virginia. Tree swallows are a socially monogamous, box-nesting species that exhibit high rates of extra-pair activity, with high variation both within and between populations, and thus are an appropriate system for this study. First, we characterized the cloacal microbiome of females by collecting cloacal swabs and determining the taxonomic composition of cloacal bacteria using 16s rRNA gene amplicon sequencing. Then, we used nestling paternity as a conservative proxy to estimate the frequency and success of extra-pair copulations, and to determine the minimum number of sexual partners per female. This study increases our understanding of how sexual activity, specifically extra-pair copulations, influences the presence, prevalence, and potential pathogenicity of cloacal microbial communities in wild birds. Additionally, this study broadens our understanding of the potential costs of different solutions to common life-history tradeoffs faced by free-living animals.

 

Implications of a changing climate on bird development

Authors: Hope, S.F.* 1, DuRant, S.E. 2, Kennamer, R.A. 3, Hopkins, W.A. 1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Tech 2. Department of Biological Sciences, University of Arkansas 3. Savannah River Ecology Lab, University of Georgia

Our changing climate may pose a threat to the early developmental environment of animals. The effect of climate change on developing reptiles is well-studied, and there is evidence that changes in incubation temperature can have substantial effects on offspring. In contrast, the effects of temperature changes on bird phenotypes have been historically overlooked because parents regulate incubation temperature. However, studies have shown that changes in the environment can affect avian parental incubation behavior, and that small changes in incubation temperature can affect avian offspring phenotypes. Yet, few studies have investigated how environmental changes may directly and indirectly influence incubation temperature, or how incubation temperature influences avian offspring behavior. We used wood ducks as a model system to address these questions. Our results show that wood duck nests with the largest clutch sizes and the lowest ambient temperatures led to the lowest incubation temperatures. We also found that ducklings incubated at 35.0 and 37.0 C exhibited bolder and more exploratory behaviors than those incubated at 35.8 C, while those incubated at 35.0 C were less successful at exiting the nest (a crucial behavior for wood duck ducklings) than those incubated at the other two temperatures. This research shows that environmental changes influence avian incubation temperature and thus, may influence offspring behaviors that are critical for survival. In this case, warming temperatures may be beneficial to developing birds, but future work should address how extreme weather events or changes in food availability due to climate change affect incubation temperature.

 

Female aggression in song sparrows is higher in urban habitats

Authors: Lane, S.J.* 1, Linkous, C.R. 1, Brewer, V. 2, Sewall, K.B. 1

Affiliations: 1. Virginia Polytechnic Institute and State University 2. New Mexico State University

Urban adapters are animals that are able to live in human-impacted areas, such as suburbs and cities. It has been hypothesized that urban adapters have behavioral phenotypes that permit them to persist in human-impacted environments. Indeed, song sparrows (Melospiza melodia) live and breed in both urban and rural habitats and previous research has shown that urban males of this species show greater territorial aggression. However, little attention has been given to female behavior across urban and rural habitats. To determine if living in urban habitats is associated with elevated aggression in female song sparrows, we simulated the intrusion of a conspecific female onto the social territory of females at two rural and two urban study sites in Blacksburg, VA. We placed a model bird 5 to 10 m of the focal bird’s nest and played one of 6 exemplars of recorded female vocalizations. For 3 minutes without the model and 6 minutes after model exposure, we measured the focal female’s distance from the speaker and the duration of vocalizations produced by the female as a measure of aggression. Female song sparrows nesting in urban habitats were more likely to respond to a simulated female intruder and showed a greater behavioral response to conspecific intrusions than did females in rural habitats. This pattern of greater female aggression in urban habitats parallels previous reports of greater territorial aggression in males and raises the hypothesis that resource competition may increase in urban environments, driving increased territorial aggression in both sexes of song sparrows.

 

Water quality at the point of use in San Rafael Las Flores, Guatemala

Authors: Marcillo, C.* 1, Garc Prado, G. 2, Copeland, N. 3, Krometis, L.A. 1

Affiliations: 1. Department of Biological Systems Engineering, Virginia Tech 2. Centro de Estudios Conservacionistas, Universidad de San Carlos de Guatemala 3. Department of Sociology, Virginia Tech

Limited information is available describing point of use water quality in rural Guatemala, particularly with respect to geologic contaminants, such as arsenic, associated with chronic health risk. This effort aimed to characterize drinking water in San Rafael Las Flores, a Guatemalan community directly adjacent to a large silver mine, to identify key contaminants of health concern. Surveys on water use and perception were conducted in 31 households, with water samples concurrently collected and analyzed for E. coli, pH, conductivity, and metals. Survey results indicated widespread distrust and dissatisfaction with in-home piped water. The majority (77%) of participants perceived their tap water to be unsafe and preferred drinking bottled water or from community springs. The majority (84%) also identified at least one aesthetic issue with their tap water (e.g. color, particulates) and only 25% of homes had continuous water service. Concerns predominantly revolved around potential health risks from arsenic and bacteria with widespread perceptions of contamination, most commonly attributed to the nearby mine. Though only two samples exceeded the 10 ppb arsenic standard, 45% were above 9 ppb. In addition, 13% of samples were positive for E. coli. Continued research is recommended to quantify potential arsenic biomarkers and critical exposure pathways. The establishment of a baseline water quality profile, confirmation of field test kit potential, and understanding local water quality concerns will permit the design of future interventions and citizen science efforts to engage the local community in discussions of potential infrastructure and land use development.

 

Ecological patterns and significance of secondary metabolites in a Neotropical shrub, Piper sancti-felicis

Authors: Maynard, L. D.* 1 and Whitehead, S. R. 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA

Rooted in place, plants often rely on secondary metabolites to mediate interactions with other organisms. Both attraction of mutualists and defense against antagonists are thought to be mediated by secondary metabolites. Piper is one of the largest genera of flowering plants, containing about 1,000 species. This study describes the secondary metabolites occurring in the infructescences of Piper sancti-felicis and their functional significance in ecological interactions. We focused on one group of compounds: alkenylphenols. We had three specific objectives: 1) to elucidate the structures of the major alkenylphenol compounds present in P. sancti-felicis; 2) to describe the natural variation in alkenylphenol composition throughout reproductive tissue development and across individual plants; and 3) to test the ecological significance of the alkenylphenols in plant defense against fungi. Results suggest that alkenlyphenol concentration in infructescences significantly differed among individual plants, developmental stages, and individual compounds. Alkenylphenol concentration was higher in ripe and unripe infructescences compared to inflorescences with high interspecific variation. Results from the microdilution bioassays revealed that as alkenylphenol concentration increases, fungal absorbance decreases. This is the first study to describe alkenylphenols in P. sancti-felicis and their ecological function as defensive secondary metabolites, possessing anti-fungal properties.

 

Terminal electron acceptor processes in metalimnetic oxygen minima changes the annual methane budget in a eutrophic freshwater reservoir

Authors: McClure R.P.* 1, Lofton M. E. 1, Schreiber M.E. 2, Little J.C. 3, and Carey C.C. 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA 2. Department of Geosciences, Virginia Tech, Blacksburg, Virginia, USA 3. Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia, USA

Freshwater reservoirs are heavily influenced by humans and commonly develop Metalimnetic Oxygen Minima (MOM) in their water columns because of different water management practices. MOM are also known to accumulate large quantities of methane (CH4) in them and change the seasonal CH4 efflux phenology. While the causes of MOM are known, less is known about their effects on CH4 production and the depletion of terminal electron acceptors (TEA) that precedes methanogenesis. MOM create distinct redox gradients in the water column that changes the distribution of CH4, but whether the CH4 is derived from methanogenesis in the MOM or from laterally entrained CH4 from methanogenesis occurring in the sediments remains unclear. We monitored profiles of CH4 and the TEAs that precede methanogenesis at five sites from the inflow to the dam in a eutrophic reservoir that develops a MOM as a result of the operation of water quality engineering systems. We observed large fluctuations in the TEA availability in the MOM and little fluctuation in TEAs at other depths in the water column that remained oxygenated. We also observed lateral entrainment of CH4 from upstream depths that coincided with the MOM. This suggests that the CH4 that is observed in MOM is from TEA depletion followed by methanogenesis in both upstream sediments and in MOM that have become anoxic. This poses new uncertainties to annual CH4 budgets in freshwater reservoirs if TEA processes that normally occur in the sediments are also occurring directly in the water column.

 

Do good neighbors make up for poor conditions? Case study on a mixed-flocking habitat specialist

Authors: McNeill, N.* 1 and Walters, J. 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA

Birds are known to form foraging flocks in numerous systems, many of which are mixed-species flocks. Individuals may choose to a mixed-flock in order to increase foraging efficiency, limit intraspecific competition, or reduce predation. In the longleaf pine system of the southeastern United States, brown-headed nuthatch (Sitta pusilla) mixed-flock during the nonbreeding season, but are subject to variable predator presence and food availability throughout this period. Furthermore, it is unknown whether this species forgoes the boundaries of its small breeding territories in order to follow mixed-species flocks. Thus, I am recording mixed-flocking behavior of brown-headed nuthatch at Marine Corps Base Camp Lejeune. Nuthatch behavior and mixed-flock interactions will be recorded. Individual nuthatches will be color banded in order to locate breeding territories and track individual movement. Additionally, I will experimentally manipulate food availability by placing feeding stations in portions of the field site. I will then record station recruitment rates and flocking behavior surrounding these stations. I expect that tendency to forage in mixed flocks is inversely correlated to food availability and individual territory quality. As food becomes scarce in winter, flock foraging reduces the predator vigilance required by each individual, increasing foraging efficiency. Determining how these factors impact nuthatch behavior will inform habitat management strategies for improved winter survival.

 

Resource Use and Interspecific Interactions in a Namibian Cavity-nesting Community

Authors: David Millican* 1, Jeff Walters 1, and Ashley Dayer 2

Affiliations: 1. Department of Biological Sciences, Virginia Tech 2. Department of Fish and Wildlife Conservation, Virginia Tech

Cavity-nesting guilds are diverse communities of animals found in forest ecosystems worldwide. Due to their dependence on tree holes for nesting, populations of these species are highly susceptible to forms of disturbance that diminish cavity availability. Namibia is the driest country in sub-Saharan Africa, with a landscape largely depauperate of large trees, the most common harborers of cavities. This community is threatened by numerous anthropogenic disturbances, including charcoal production, altered grazing and fire regimes, and increasingly frequent and severe droughts caused by climate change. To aid the conservation of this threatened community, we have embarked on a multi-year nest-web analysis to quantify community structure. Through this analysis, we seek to describe the type of nest cavities available in the landscape, species-specific resource use preferences, and direct and indirect interactions between community members. Quantifying community structure willprovide important information for land use managers who want to mitigate impacts of anthropogenic disturbance on this community. To aid conservation of this community, we have alsoembarked on a sociological study to identify a potential flagship species. By using emotional prompts to identify wildlife perceptions of local communities, we hope to identify a potential flagship species that will effectively bring awareness to the plights facing this community, and to encourage behavior change in the form of preserving large, cavity-bearing trees. By combining ecological and sociological research, we hope to generate recommendations for both ecological management as well as sociological strategies to generate local support for a conservation campaign.

 

Male Red-cockaded Woodpecker dispersal habitat analysis

Authors: Leah D. Novak* 1, Jeffrey R. Walters 1, and Dylan Kesler 2

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA 2. The Institute for Bird Populations, Point Reyes Station, CA

Natal dispersal is the movement of individuals from a birth site to a breeding site. Juveniles often foray before dispersal, that is explore outside their natal territory to gather information from the environment and conspecifics regarding habitats and conditions. Individuals choose specific habitat characteristics to travel through and explore while foraying. Understanding what habitat characteristics an individual uses while foraying is key for identifying important resources which promote exploration and movement during dispersal, and for creating and implementing effective management strategies especially for endangered species, such as the Red-cockaded Woodpecker (RCW). The cooperatively breeding RCW is a federally listed endangered species endemic to open, southern pine savannah in the Atlantic and Gulf Coastal Plains of the United States. Juvenile male RCWs have two dispersal syndromes: they can either delay dispersal and remain on their natal territory as non-breeding helpers or disperse their first year in search of territories with open breeder positions. Dominance within broods plays an important role in determining which dispersal strategy a juvenile male will use. Dominant males almost always remain as helpers, while subordinate males disperse their first year. Despite understanding dispersal outcomes of male and female RCWs, very little is known about the dispersal process and behavior of males. Therefore, I followed dominant and subordinate juvenile, and adult helper males using radio-telemetry, and recorded GPS coordinates and behavioral observations to determine dispersal behavior and habitat use. Overall, juvenile and helper males tended to use habitats that had high quality foraging resources (older, larger longleaf and loblolly pines) and were hidden from other RCW families‚ a group of cavity trees (called a cluster), though male RCWs did seek out other RCW clusters if the family group that guarded that cluster was not present.

 

Predicting golden-crowned sifaka (Propithecus tattersalli) density from habitat and nutritional variables

Authors: Semel, B.P.* 1, Karpanty, S.M. 1, Semel, M.A. 2, Walters, G.T. 1, Ranaivoson, T.N. 3, and Rothman, J.M. 4

Affiliations: 1. Dept. of Fish and Wildlife Conservation, Virginia Tech  2. Dept. of Biological Sciences, Virginia Tech  3. Dept. of Zoology and Animal Biodiversity, University of Antananarivo  4. Dept. of Anthropology, Hunter College of CUNY, NY

Understanding relationships between animal populations and nutritional variables is important for effectively managing threatened animal populations in dynamic environments. Madagascar’s lemurs are threatened by forest destruction, yet we know very little about how populations will respond to the additional threat posed by climate change. In northeastern Madagascar, critically endangered golden-crowned sifakas (Propithecus tattersalli) live in dry, deciduous to humid rain-forests across a unique biogeographic transition zone. This makes them an ideal case study in which to examine the effects of climate-mediated forest type variables and plant nutrition on sifaka population densities. Specifically, we will investigate the relationships between tree species densities, canopy cover, species diversity, normalized difference vegetation index (NDVI), available plant fiber, energy, and protein values on sifaka densities in ten different forest fragments. Results will help us to better understand how forest type and nutritional variables impact lemur populations. This will help conservation managers to protect key forest habitats and to select the most important tree species for ongoing reforestation efforts. Future work will employ climate models to predict future forest cover types and ultimately, future sifaka population abundance across the species’ range.

 

Impact of habitat type and disturbance level on golden-crowned sifaka (Propithecus tattersalli) social cohesion and ranging behavior

Authors: Meredith Semel* 1, Julie Ratovoson 2, Ignacio Moore 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech 2. Biology and Conservation, University of Antananarivo

Madagascar, an island off the coast of southeast Africa, is one of the world’s richest biodiversity hotspots, yet little is known about how habitat degradation will affect imperiled species. Golden-crowned sifakas (Propithecus tattersalli), listed as critically endangered on the IUCN red list, are folivorous, group living primates endemic to forests of northern Madagascar. Golden-crowned sifakas display a flexible behavioral strategy called fission-fusion, which results in individuals periodically separating from group members (fissions) and rejoining after temporal and spatial separation (fusions). We are seeking to examine how fragmentation and landscape heterogeneity influence fission-fusion dynamics, ranging behavior, and overall social cohesion in this species. To do this, we completed 7 full-day behavioral follows for nine groups of golden-crowned sifakas in an array of rainforest and dry forest fragments surrounding Daraina, Madagascar (August-December 2018). Using scans at ten-minute intervals, we recorded activity, height, feeding information, nearest neighbor proximity, and group spread. Overall, we found that fragment type resulted in a significant amount of variance on group spread and territory size; with sifakas displaying decreased group cohesion in rainforest fragments, possibly due to decreased food availability and separating from group members to acquire necessary nutrients. Now that we have an understanding of P. tattersalli behavior we will be employing the use of novel tracking devices to automate our data collection and more effectively collect group cohesion and ranging data.

 

Scientists’ roles in policy-making

Authors: Seo, H.* 1

Affiliations: 1. School of Public and International Affairs, Virginia Tech

This paper explores scientists’ roles in policy-making based on literature review with the aim of gaining insights into how policy processes might be enhanced through better science-policy interactions. Integrating scientific knowledge into policy-making and management processes is challenging because of the inherently different purposes, assumptions, and framing of scientific information and policy information (Innes & Booher, 2010). When it comes to research about environmental issues such as biodiversity and conservation, it is even more difficult to use scientific research to inform policy-making and implementation because these environmental issues are particularly complex in nature, involving uncertainty, complexity, diverse conflicting values and multiple objectives in various sectors; science alone cannot provide simple, optimal solutions (Young et al., 2014). To address these challenges, this paper starts with two paradigms of science-policy interactions which determine scientists’ roles required in society: the democratic and technocratic approaches. Further, it examines theories about boundary work at science-policy interfaces, and reviews existing typologies of scientists roles. It concludes with a discussion of future direction for research.

 

Do Roots Bind Soil? Comparing the Physical and Biological Role of Roots in Fluvial Streambank Erosion Resistance

Authors: Smith, D.J.* 1 and Thompson, T.M. 1 

Affiliations: 1. Department of Biological Systems Engineering , Virginia Tech

Today, it is recognized that plant roots affect streambank erosion through various processes, including: 1) physical binding of soil particles by roots, 2) gluing soil particles together due to the release of extracellular polymeric substances (EPS) by soil microorganisms, and 3) alterations to the streambank fluvial boundary layer. However, the relative importance of these mechanisms is not fully understood. To quantify the effects of roots and soil microbial communities on erosion resistance, laboratory testing was conducted using a jet erosion test device‚ an erosion measurement tool used measure soil erodibility and critical shear stress. Erosion resistance measurements were also correlated with plant, soil, and microbial parameters, including EPS, aboveground biomass, root length density (RLD), and aggregate stability. The experimental setup included five treatments: 1) sterile soil, 2) sterile soil with synthetic roots, 3) inoculated soil, 4) inoculated soil with synthetic roots, and 5) inoculated soil with live roots. Critical shear stress was significantly increased in Treatments 2, 4, and 5 compared to Treatment 3 by 67%, 75%, and 79%, respectively. As RLD and aggregate stability increased in vegetated samples (Treatment 5), soil critical shear stress significantly increased as well. However, soil erodibility was also significantly increased by 33% in Treatment 4 compared to Treatment 1. In addition, Treatment 5 saw a significant 10% decrease in aggregate stability in samples compared to all other treatments. These results suggest that the physical presence of fibers or the biological activity of microorganisms alone may not significantly impact soil resistance to fluvial erosion.

 

The Screech Owl Nest Web: A New Opportunity for Citizen Science in Montgomery County, Virginia

Authors: Ben Vernasco* 1 and Ignacio Moore 1 

Affiliations: 1. Department of Biological Sciences, Virginia Tech

Citizen science projects rely upon the public to assist in the scientific process and these projects are known to have a number of benefits. Citizen science 1) promotes engagements between the public and scientists, 2) increases scientific literacy and 3) expands data collection opportunities to a level beyond what is possible by a single researcher. Birds that nest in artificial nest boxes present a unique opportunity for citizens to engage in the scientific process by providing a nesting cavity on their property and monitoring the nesting progress of the inhabitants. Here, I propose to establish a new citizen science project for Montgomery County that entails establishing and monitoring nest boxes specifically designed for Eastern Screech Owls (Megascops asio). Eastern Screech Owls are currently declining in parts of their range, including Virginia, and a lack of nesting cavities is a contributing factor. The owls are known to occupy artificial nest boxes in the suburban and rural habitats present in Montgomery County. With this program, we can monitor the nesting success of this charismatic bird. Additionally, the proposed project can also address questions related to breeding phenology, population demography, dispersal behaviors, and the effects of urbanization on wildlife. Beyond the local level, participants can submit their data to the NestWatch Program established by the Cornell Lab of Ornithology. Overall, the proposed project can contribute to the conservation of a declining species, establish a new study system for the GCC community, and, most importantly, engage the public in the scientific process.

 

Estimating Occupational Heat Exposure from Personal Sampling of Public Works Employees in Birmingham, Alabama

Authors: Suwei Wang* 1,5, Molly B. Richardson 1, Connor Y.H. Wu 2, Carly D. Cholera 3, Claudiu T. Lungu 3, Benjamin F. Zaitchik 4, Julia M. Gohlke 1

Affiliations: 1. Department of Population Health Sciences, Virginia Tech, Blacksburg, VA 2. Department of Geospatial Informatics, Troy University, Troy, AL 3. School of Public Health, University of Alabama at Birmingham, Birmingham, AL 4. Department of Earth & Planetary Sciences, Johns Hopkins University, Baltimore, MD 5. Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA

Excessive occupational heat stress has been associated with increased mortality and injury rates. Wet bulb globe temperature (WBGT) index is widely used to assess heat stress and recommend work-rest cycles combined with metabolic rates of workers. Currently, estimates of WBGT use meteorological data from nearby weather stations (WS), but likely do not reflect actual environmental conditions at a specific workplace. This study evaluated whether using thermometers clipped on workers shoes would result in different work-rest schedules compared to using area-level meteorological data alone.

 

Spatial variability in oligotrophic lake metabolism may indicate trophic state change due to localized stream loading

Authors: Nicole K. Ward* 1, Jennifer A. Brentrup 2, David C. Richardson 3, Kathleen C. Weathers 4, Cayelan C. Carey 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA 2. Department of Biological Sciences, Dartmouth College, Hanover, NH, USA 3. Biology Department, SUNY New Paltz, New Paltz, NY, USA 4. Cary Institute of Ecosystem Studies, Millbrook, NY, USA

Local land-use and global climate change are rapidly degrading oligotrophic lakes. Robust water quality indicators are needed to determine whether oligotrophic lakes are maintaining their low-nutrient state. Lake metabolism, the balance of carbon production and respiration, is an integrated ecosystem metric that may indicate impending ecosystem shifts to a meso- or eutrophic state. Ecosystem metabolism modeled from one deep site within a lake is often assumed to be representative of the entire lake; little is known about the relationship between lake metabolism estimates at near-shore sites and nutrient loading from the nearest inflow. Here, we ask: How do summer lake metabolism estimates at near-shore sites (4-7 m deep) compare to a single deep-site (13 m deep) estimate? We addressed this question in oligotrophic Lake Sunapee, New Hampshire (USA). We used high-frequency measurements of dissolved oxygen, water temperature, and light to estimate metabolism at three near-shore sites and one deep-site. We also measured stream discharge and nutrient concentrations in the closest inflow streams to each near-shore lake site to estimate localized nutrient loading. Net ecosystem metabolism at Lake Sunapee’s deep-site was consistently positive (range = 0.01‚ 0.5 mg-O2/L/day) whereas all three near-shore sites averaged near zero net ecosystem metabolism (range = -0.4 – 0.3 mg-O2/L/day). Localized stream nutrient loading was positively correlated with daily maximum GPP and R rates. Linking spatially variable lake metabolism to heterogeneous nutrient loading provides insight into how lakes integrate catchment land use, providing an indicator of impending shifts in lake trophic state.

 

How can the cavity nest-web inform conservation of the endangered Bahama Swallow (Tachycineta cyaneoviridis)?

Authors: Maya Wilson* 1 and Jeffrey R. Walters 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech

The Bahama Swallow (Tachycineta cyaneoviridis) only breeds in the northern Bahamas, and is considered endangered due to decline in its population. However, causes of population decline are unknown. As an obligate secondary cavity nester, the swallow requires other species or processes to create cavities in which to nest. We constructed a cavity nest-web to investigate whether nest site availability and interactions between swallows and other cavity-nesting species could provide insight into causes of decline and the design of conservation strategies. We conducted surveys to assess the availability of cavity-nesting resources in Caribbean Pine (Pinus caribaea) forest and other habitats. We also examined potential competition by locating nests of all other cavity-nesting species. We measured reproductive success by monitoring swallow nests in different cavity types. Swallows built nests in several cavity types, primarily those excavated by Hairy Woodpeckers (Picoides villosus) and West Indian Woodpeckers (Melanerpes superciliaris). La Sagra’s Flycatchers (Myiarchus sagrae) were the only other secondary cavity nesters that utilized the sparsely distributed pine snag cavities, which are excavated by Hairy Woodpeckers. Other cavity types were in anthropogenic structures and were concentrated in developed areas, where swallows face potential competition with American Kestrels (Falco sparverius), and non-native House Sparrows (Passer domesticus) and European Starlings (Sturnus vulgaris). Reproductive success was high during all nest stages in pine snags, while success in other cavity types appeared to vary. These findings indicate that managing for pine snags and the presence of Hairy Woodpeckers in the pine forest may be crucial to Bahama Swallow conservation.

 

Convergent evolution and high cranial disparity in the close relatives of archosaurs as demonstrated in Doswellia sixmilensis (Archosauriformes: Proterochampsia)

Authors: Wynd, B. M.* 1, Nesbitt, S. J. 1, Stocker, M. R. 1, Heckert, A. B. 2

Affiliations: 1. Department of Geosciences, Virginia Tech 2. Department of Geological and Environmental Sciences, Appalachian State University

The Triassic Period (252 – 200 Ma) records a great expansion of reptile diversity and disparity, particularly in skull morphology. Close relatives of archosaurs (group including birds and crocodiles) exhibit substantial range in cranial disparity, especially by species shortening or elongating the skull. This disparity is exemplified in North American Late Triassic proterochampsians by short-faced and long-faced doswelliids. To investigate skull elongation and character evolution in proterochampsians, we evaluate the taxon, Doswellia sixmilensis, from the Late Triassic of New Mexico. We redescribe D. sixmilensis based on repreparation of the skull material and reinterpret what was previously regarded as the antorbital fenestra to be the orbit. Because of this, the identification of bones and the taxon diagnosis must be substantially modified. We score D. sixmilensis into a phylogeny of archosaurs and their close relatives, consisting of 676 characters and 109 taxa. We recover Doswelliidae as a monophyletic clade nested within the South American Proterochampsidae. This challenges previous interpretations of the Doswelliidae and suggests previously unrecognized cranial disparity within Proterochampsidae. To reconstruct archosauromorph cranial disparity, we place D. sixmilensis and other proterochampsians into a similarity analysis of 36 taxa and 42 cranial characters using a non-metric multidimensional scaling ordination plot. We find that early diverging proterochampsians explore regions of morphospace explored only by long-snouted taxa (archosaurs and their close relatives), and are disparate from other skull forms. This indicates that archosaur relatives experimented with the anterior half of their skulls with a combination of unique and convergent characters present in the earliest archosaurs.

fossil

3rd Annual

Interfaces of Global Change Graduate Research Symposium

April 19, 2018
Fralin Hall

The Third annual Interfaces of Global Change (IGC) Graduate Research Symposium was held on April 19, 2018 in Fralin Hall. The gathering provides a forum for students and faculty to interact and explore connections between labs across campus. Record numbers were set for participation this year, and the day included 13 oral presentations and a poster session by 27 students.

The symposium highlighted the latest research from the program’s graduate student fellows, whose collective work addresses critical global changes impacting the environment and society. This includes problems surrounding climate change, pollution, invasive species, disease, and habitat loss.

Platform awards for Best Presentation were selected for the top three oral presentations. This year’s winners were:

First Place Ryan McClure, “Hypolimnetic oxygenation increases methane ebullition in a eutrophic drinking water reservoir”

Second Place Tamara Fetters, “A summary of my dissertation work on changes in physiology and life history in an invasive lizard”

Third Place Ernie Osburn, “Soil microbial response to Rhododendron maximum understory removal in Appalachian forests”

(Left to right) GCC Director, Bill Hopkins; IGC Fellows: Tamara Fetters, Ernie Osburn, Ryan McClure; IGC Director, Jeff Walters.

Kudos to all the student participants!  Your work is truly inspiring, important and impactful to the Virginia Tech community and beyond.  Thank you to the GCC Faculty and other researchers on campus who came out to show their support for the IGC Fellows!

See more photos from the Symposium on FLICKER

Detailed AGENDA PDF

Thursday, April 19, 2018

9:15 a.m.         Poster setup; Fralin Hall Atrium

9:55 a.m.         Welcome (Jeff); Fralin Auditorium

10:00 a.m.       Session 1 (S1); Session Chair: Angie Estrada

10:00 a.m.       S1 Talk 1 Ben Vernasco

10:15 a.m.       S1 Talk 2 Ryan McClure

10:30 a.m.       S1 Talk 3 Fadoua El Moustaid

10:45 a.m.       S1 Talk 4 Carl Wepking

11:00 a.m.       Break and poster viewing

11:30 a.m.       Session 2 (S2); Session Chair: Jon Doubek

11:30 a.m.       S2 Talk 1 Maya Wilson

11:45 a.m.       S2 Talk 2 Zach Gajewski

12:00 p.m.       S2 Talk 3 Brenen Wynd

12:15 p.m.       S2 Talk 4 Tamara Fetters

12:30 p.m.       Lunch and poster viewing; Fralin Atrium

1:30 p.m.         Session 3 (S3); Session Chair: Derek Hennen

1:30 p.m.         S3 Talk 1 Mike Graham

1:45 p.m.         S2 Talk 2 Bennett Grooms

2:00 p.m.         S2 Talk 3 Gifty Anane-Taabeah

2:15 p.m.         S2 Talk 4 Ernie Osburn

2:30 p.m.         S2 Talk 5 Zach Martin

2:45 p.m.         Poster Reception (students by posters)

3:45 p.m.         Platform Award Announcements

4:00 p.m.         Symposium Adjourns

All IGC fellows are encouraged to present their work at the symposium. Fellows have the option of presenting either a poster or a talk. Awards will be given for best talks.

Abstracts for talks and posters should be submitted to Jessica Zielske (jcoker@vt.edu). Each abstract should contain:

  1. Title
  2. Authors and Affiliations (e.g., Department and University)
  3. An abstract not to exceed 250 words in length

For posters: maximum poster size is 40″ x 60″.  An easel and backboard will be provided.

Platform Session 1   10:00 – 11:00 a.m.
Session Chair: Angie Estrada

 

Causes and consequences of the cooperative display behavior of wire-tailed manakins

Authors: Ben Vernasco 1, Brent Horton 2, T. Brandt Ryder 3, Ignacio Moore 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. Department of Biology, Millersville University 3. Smithsonian Migratory Bird Center

Manakins of the family Pipridae are a fascinating family of birds known for their bright plumage and complex courtship displays. Among male manakins, variance in reproductive success has been found to be dependent on a male’s display performance, and in the case ofspecies that exhibit male-male coordinated courtship displays, their ability to form and maintain social bonds with display partners. Accordingly, elucidating the proximate causes and consequences of individual variation in reproductive and cooperative courtship behavior can broaden our understanding of the evolution of cooperative behavior. Here, we quantified social and hormonal correlates of individual variation in display behavior of territory-holding wire-tailed manakins by using video recordings of and blood samples collected from territory-holding males. Our results show that males with a higher proportion of cooperative displays performed longer display bouts and also spent a higher proportion of time displaying. However, males with high circulating testosterone levels engaged in fewer cooperative display bouts suggesting that high levels of testosterone may interfere with effective cooperative behavior. Our results suggest that individual differences in circulating testosterone levels likely play an important role in mediating a male’s ability to form and maintain social partnerships and, thus, indirectly mediates individual variation in male reproductive behavior. This research ultimately adds to our knowledge about the evolution of cooperative courtship behavior and the proximate mechanisms that mediate individual variation in both reproductive and cooperative behavior.

Hypolimnetic oxygenation increases methane bubble fluxes in a eutrophic drinking water reservoir

Authors: Ryan P. McClure 1, Mary E. Lofton 1, Kathryn M. Kruger 2, Shengyang Chen 3, John C. Little 4, Madeline E. Schreiber 2, Cayelan C. Carey 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA 2. Department of Geosciences, Virginia Tech, Blacksburg, Virginia, USA 3. School of Civil Engineering, University of Sydney, Sydney, NSW 2006, Australia 4. Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia, USA

Freshwater reservoirs contribute a considerable source of methane (CH4) to the atmosphere via bubble fluxes from the sediments (ebullition). Despite their importance, the controls of CH4ebullition patterns remain poorly understood, especially in reservoirs managed for drinking water. Throughout the stratified period of 2017, we measured ebullition rates at 20 sites in Falling Creek Reservoir, a small eutrophic drinking water reservoir in Virginia, USA that is managed with a hypolimnetic oxygenation system (HOx) to improve water quality. Ebullition rates across the reservoir experienced predicted seasonal trends that increased with elevated sediment temperatures until fall turnover. However, contrary to previous studies that observed the highest ebullition rates occurring in the shallowest sites of waterbodies with elevated sediment temperatures, we also observed elevated ebullition rates in the deepest site of the reservoir, likely a result of HOx operation. Activation of the HOx system mixed the sediments at the deep hole, generating enough mixing near the sediments to release ebullition bubbles stored in the anoxic sediments that were able to rise to the surface. Thus, while oxygenation systems are generally thought to decrease net CH4emissions by promoting CH4oxidation, our results suggest that in some reservoirs, oxygenation may actually stimulateebullition. As reservoir construction and management increases globally, it is imperative to understand how their drinking water management may affect CH4emissions in the future.

A mathematical modeling approach to the Cort-Fitness Hypothesis

Authors: Fadoua El Moustaid 1 Ignacio T. Moore 1, Samuel J. Lane 1 Leah R. Johnson 1,2

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. Department of Statistics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

The Cort-Fitness Hypothesis continues to be challenged by experimental studies. The inconsistency of the relationship between cort levels and the relative fitness of individuals and populations often results in the failure of the hypothesis. Meanwhile, other studies provide support for the hypothesis, hence a deeper understanding of the mechanisms underlying the hypothesis is needed. Motivated by reviews on studies testing the Cort-Fitness Hypothesis, we propose a mathematical model representing the link between, cort levels, environmental challenges, and fitness. Our model explores how variation in the predictability and intensity of environmental challenges, reproduction strategies, and fit- ness metrics all contribute to the cort-fitness relationship. We provide qualitative results showing the cort-fitness relationship for different environmental scenarios as well as how the model can be used to inform cort-fitness future experiments.

Livestock antibiotics alter soil microbial communities and ecosystem function

Authors: Carl Wepking 1, Brian Badgley 2, Jeb Barrett 1, Katharine Knowlton 3, Kevan Minick 4, Partha Ray 5, Michael Strickland 1,6

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic and State University 2. Department of Crop and Soil Environmental Sciences, Virginia Polytechnic and State University 3. Department of Dairy Science, Virginia Polytechnic and State University 4. College of Natural Resources, NC State University 5. School of Agriculture, Policy and Development, University of Readin 6. Department of Soil and Water Systems, University of Idaho

The health crisis resulting from the declining effectiveness of antibiotics has called all antibiotic usage into question, including their use in livestock production – accounting for 80% of domestic use. Between 40-95% of antibiotics administered to livestock enter the environment via manure at a rate of up to 14-million kg-yr​-1. Previous work has shown that additions of manure from antibiotic-treated cattle can affect microbial communities compositionally, genetically, and physiologically. Most importantly, changes in antibiotic resistance gene (ARG) abundance were found to be associated with microbial stress, resulting in altered ecosystem functioning. To better understand the relative contribution of manure and antibiotics, an experiment was established where plots were amended with manure from cattle treated with one of two types of antibiotics, or untreated cattle at a rate of 650-g m-2 month -1for three years. Each spring, plots were pulse-labeled using 13C and15N. Plots were harvested in successive days to determine how these treatments affect the microbial community and elemental cycling. Initial findings suggest that antibiotic-laden manure impacts a number of important soil microbial parameters. Manure from cattle treated with pirlimycin elicited an ~6,000 kg ha-1y-1increase in respired carbon compared to cephapirin-laden manure. Analysis of the 13C and 15N pulsed into the system also revealed that the antibiotic treatments do alter elemental cycling in soils. Although analysis is ongoing, initial results from this study show that antibiotics can impact microbial communities and soil functioning, however effects are not uniform, instead depending on the antibiotic in question.

Platform Session 2   11:30 a.m. – 12:30 p.m.
Session Chair: Jon Doubek

 

How can the cavity nest-web inform conservation of the endangered Bahama Swallow (Tachycineta cyaneoviridis)?

Authors: Maya Wilson 1 and Jeffrey R. Walters 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

The Bahama Swallow (Tachycineta cyaneoviridis) only breeds in the northern Bahamas, and is considered endangered due to decline in its population. However, causes of population decline are unknown. As an obligate secondary cavity nester, the swallow requires other species or processes to create cavities in which to nest. We constructed a cavity nest-web to investigate whether nest site availability and interactions between swallows and other cavity-nesting species could provide insight into causes of decline and the design of conservation strategies. We conducted surveys to assess the availability of cavity-nesting resources in Caribbean Pine (Pinus caribaea) forest and other habitats. We also examined potential competition by locating nests of all other cavity-nesting species. We measured reproductive success by monitoring swallow nests in different cavity types. Swallows built nests in several cavity types, primarily those excavated by Hairy Woodpeckers (Picoides villosus)and West Indian Woodpeckers (Melanerpes superciliaris). La Sagra’s Flycatchers (Myiarchus sagrae) were the only other secondary cavity nesters that utilized the sparsely distributed pine snag cavities, which are excavated by Hairy Woodpeckers. Other cavity types were in anthropogenic structures and were concentrated in developed areas, where swallows face potential competition with American Kestrels (Falco sparverius), and non-native House Sparrows (Passer domesticus) and European Starlings (Sturnus vulgaris). Reproductive success was high during all nest stages in pine snags, while success in other cavity types appeared to vary. These findings indicate that managing for pine snags and the presence of Hairy Woodpeckers in the pine forest may be crucial to Bahama Swallow conservation.

 

Varying Temperature Effects on the Growth of the Amphibian Chytrid Fungus

Authors: Zach Gajewski 1 and Leah Johnson 2

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. Department of Statistics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Temperature is an important factor in many disease systems by influence traits like, growth rate or reproductive rate. However, the role of temperature in these systems is often studied in an artificial way, not allowing the temperature to change. Relating this data back to a more natural temperature scenario is difficult and relies on inaccurate methods. Temperature is especially important in the amphibian chytrid fungus system (Batrachochytrium dendrobatidis), where cooler temperatures lead to higher infection rates. With temperature being a main factor in many disease systems, it is important to develop accurate methods to relate constant temperature experiments to a varying temperature environment.

One of the most common methods used to take constant temperature experiments to predict traits in a varying temperature regime is rate summation. This method has not been widely tested to see when and where this technique works. To test this method in the amphibian chytrid fungus system we fit a logistic growth model to optical density data. The logistic growth rate of the growth model was plotted against temperature and used to fit a Briere curve. Using the Briere curve, we can use rate summation to make predictions about Bd growth in the varying temperature conditions. When comparing the prediction against varying temperature growth data we found that rate summation over predicted the growth of Bd using constant temperature.

 

Diversity of Chondrichthyes through the uppermost Cretaceous Hell Creek Formation of Garfield County, Montana, with implications for the Cretaceous-Paleogene mass extinction in freshwater environments

Authors: Brenen M. Wynd 1, David G. DeMar Jr. 2, Gregory P. Wilson 2

Affiliations: 1. Department of Geosciences, Virginia Tech Polytechnic and State University, Blacksburg, VA 2. Department of Biology, University of Washington

The Cretaceous-Paleogene (K-Pg) mass extinction is a well-studied mass extinction event, but there remain two main competing hypotheses that explain the diversity changes observed in the fossil record: (1) a sudden and rapid loss of many species at the K-Pg boundary (ca. 66 Ma) caused by a Bolide impact (Chicxulub); and (2) vertebrate biodiversity declines prior to and at the K-Pg boundary due to multiple factors (e.g., changing sea levels, volcanism, bolide impact). To examine these two hypotheses, we examined the diversity changes of Chondrichthyes (sharks and relatives) from freshwater deposits of the Hell Creek Formation (HC), leading up to the end of the Cretaceous. We analyzed diversity dynamics using 1065 fossil teeth stored at the University of Washington, Burke Museum of Natural History and Culture and the University of California Museum of Paleontology from eight vertebrate microfossil localities stratigraphically distributed throughout the HC. Our samples include the occurrences of three new shark species based on morphologically distinct teeth, as well as a novel batoid (i.e., rays). We also report on the first sand tiger shark from the HC, as well as a tentative carchariniform tooth, indicating a freshwater incursion by these, otherwise, marine taxon. Using raw taxonomic, standing, subsampled analytic rarefied, and shareholder quorum subsampling (SQS) richnesses, our study shows richness increases to seven species between 30.5 and 35 m above the Hell Creek/Fox Hills contact (HFC). Heterogeneity indices surrounding this interval indicate a faunal restructuring in which relative abundance of the guitarfish Myledaphus pustulosus starkly declines throughout the remainder of the HC section resulting in more species-even localities. Species diversity decreases between 35 and 83.2 m above the HFC and rise to a peak of nine species at 84.3 m above the HFC (4.2 m below the Hell Creek/Tullock contact). Nine of the ten HC chondrichthyans extend into the last 10 m of the HC, showing a very rapid, abrupt extinction in HC chondrichthyans. These changes in diversity resemble the abrupt extinction patterns shown for mammals (terrestrial) rather than the stepwise extinction patterns shown for amphibians (aquatic) although the later shared the same environments. Changes in chondrichthyan community structure and diversity in relation to other HC taxa indicate a unique and complex pattern of extinction, one suggesting that HC chondrichthyans were acted upon by a variety of selection pressures, supporting a multi-cause extinction hypothesis.

 

Physiological and life-history trait variation in an invasive lizard, Anolis sagrei

Authors: Tamara Fetters 1, William Hopkins 2, Joel McGlothlin 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

During biological invasions, non-native invaders often experience environments that differ substantially from those found in their native range; these novel conditions can impose strong directional selection and lead to rapid phenotypic divergence between native and invasive populations. The brown anole (Anolis sagrei) is a small lizard native to Cuba and the Bahamas that has invaded the southeastern United States over the past century. Native and invasive populations experience different climatic variables with more northern invasive populations experiencing lower mean annual temperatures and greater seasonal variation than more southern native populations. We hypothesized that invasive populations would subsequently display phenotypic differentiation in physiological and life-history traits in order to conform to the newly encountered environment, and further that these trait changes would result from genetic adaptation. We collected brown anoles from native populations in the Bahamas and invasive populations in the southeastern United States ranging from southern Florida to Georgia. We then measured a suite of physiological and life-history traits in both the wild-caught adults and their lab-reared offspring. We found that physiological and life history traits do differ across native and invasive populations, but that genetic adaptation does not underlie all trait changes equally. Our results indicate that the divergence of physiological and life-history traits may have facilitated the successful establishment and expansion of the brown anole.

Platform Session 3   1:30 p.m. – 2:45 p.m.
Session Chair: Derek Hennen

 

Soil tillage, carbon, and global change

Authors: Michael W. Graham 1,2, Megan E. O’Rourke 2, R. Quinn Thomas 3, Brian D. Strahm 3, James B. Campbell 4

Affiliations: 1. Geospatial and Environmental Analysis Program, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. Dept. of Horticulture, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 3. Dept. of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 4. Dept. of Geography, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Soil tillage is a ubiquitous agricultural management practice on croplands globally. Tillage impacts climate via biogeochemical processes by accelerating decomposition of soil carbon (C) and releasing of CO2. Conservation tillage practices (NT), which reduce soil C decomposition and leave more crop residue on the soil surface compared to more intensive, conventional tillage practices (CT), have potential to serve as a climate change mitigation measure through increased soil C storage on agricultural land. But, much is unknown regarding the direction and magnitude of tillage effects on climate, and effects of NT on C storage may be quite variable. Earth system models (ESM) are fully-coupled models of the entire Earth system capable of comprehensively representing all physical processes affecting climate and interactions thereof. ESMs can represent the terrestrial carbon cycle and carbon-climate feedbacks, and ESM outputs form the basis of international agreements and reports on climate change. Few studies have conducted ESM simulations to comprehensively assess the effects of different tillage practices on global climate. This research will elucidate the effects of different tillage practices on soil C and emissions by simulating soil tillage in a major ESM, the Community Terrestrial Systems Model (CTSM). Effects of intensive CT practices on soil C cycling will be evaluated by enhancing soil decomposition rates over the historical time period (1850-2014). The mitigation potential of changing from CT to NT practices will be assessed by reducing decomposition rates relative to those under CT for a future climate change scenario (2014-2100).

 

The human dimensions of wildlife recreationists: understanding the role of wildlife recreation in conservation and management

Authors: Bennett P. Grooms 1 and Ashley A. Dayer 1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Wildlife recreationists are important constituents of state wildlife agencies. Participation in wildlife recreation has been linked to pro-environmental behaviors and can facilitate positive collaborations between recreationists and state wildlife agencies. As such, state wildlife agencies are interested in engaging wildlife recreationists to aid in conservation and management. However, the ability of state wildlife agencies to engage wildlife recreationists depends on their understanding of the needs, attitudes, and behaviors of wildlife recreationists. Social factors, such as motivations, trust, and preferences, can influence wildlife recreationists’ willingness to engage in conservation behaviors and support state wildlife agency actions. Further, these social factors may differ among and within wildlife recreation groups.

We have begun using a mixed methods approach to study wildlife recreationists in Virginia. Data collection is occurring in two phases, beginning with a series of 8 focus groups targeting 4 recreation strata: wildlife viewers, birdwatchers, hunters, and anglers. Focus groups (i.e., group interviews) are informing questions on a statewide online survey that will be implemented in a second phase of the research. Findings will inform the development of a recreation management plan to aid the Virginia Department of Game and Inland Fisheries in better engaging and serving the diversity of wildlife recreationists in conservation and management.

 

 

The effect of aquaculture on the genetic purity of natural populations of Nile tilapia Oreochromisniloticusin Ghana

Authors: Gifty Anane-Taabeah 1, Emmanuel A. Frimpong 1, Eric Hallerman 1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Aquaculture has the potential to provide food on a sustainable basis for sub-Saharan Africa.However, the rapid expansion of aquaculture in the region could threaten the local adaptation and genetic diversity within wild populations if farmers import and grow alien strains deemed to have growth advantage over native strains. We investigated the genetic background of aquaculture strains of Nile tilapia Oreochromis niloticusin Ghana and assessed the genetic impact of aquaculture on wild populations using samples from selected farms on the Volta Lake and wild populations from the Volta River. We analyzed mitochondrial DNAsequences from the D-loop regionand the ND1 geneamong populations and compared them with GenBank sequences of the Genetically Improved Farmed Tilapia (GIFT) strain of O. niloticusand its derivatives, and USA grocery tilapia samples with labels from China and Ecuador.We also screened the populations at ten nuclear microsatellite loci. Our preliminary analysis revealed a “Ghana cluster” comprising both farmed and wild samples, which were genetically distinct from the GIFT and related strains. We also found that at least one farm had samples that clustered with the GIFT and related strains. Furthermore, some wild samples clustered with the GIFT and related strains, suggesting that the GIFT strains being farmed in Ghana have already escaped into the wild. Ongoing analysis of the nuclear microsatellite data should provide insight into the degree of genetic mixing of the GIFT strains and natural populations of O. niloticusin Ghana and help prioritize populations for conservation actions.

 

Soil microbial response to Rhododendron maximum removal in Appalachian forests

AuthorsErnest D Osburn 1, Jennifer D Knoepp 2, Chelcy F Miniat 2, Katherine J Elliott 2, J E Barrett 1

Affiliations1. Biological Sciences, Virginia Tech 2. USDA Forest Service, Coweeta Hydrologic Laboratory, Otto, NC

Rhododendron maximumis a native evergreen shrub that has expanded in Appalachian forests following declines of American Chestnut and Eastern Hemlock. Rhododendronis of concern to forest managers because it slows forest succession by limiting light and soil nutrient availability needed for tree seedling recruitment. We are testing Rhododendroncanopy removal with and without organic soil (O-horizon) removal as a management strategy to promote forest recovery. We hypothesized that Rhododendroncanopy removal in combination with O-horizon removal would increase soil nitrogen (N) availability, resulting in a shift towards a bacterially-dominated microbial community and increased microbial demand for carbon (C), leading to higher activities of microbial enzymes associated with C acquisition. Two years following canopy removal and one year following O-horizon removal, we sampled soils and found that dissolved organic carbon (DOC), microbial biomass, and soil N all increased with Rhododendroncanopy + O-horizon removal. Additionally, we observed increases in C-acquisition enzymes involved in degrading cellulose (β-glucosidase) and hemicellulose (β-xylosidase) in soils with canopy and O-horizon removed. Contrary to our predictions, we did not see treatment effects on bacterial dominance, though microbial communities from all treatments shifted towards fungal dominance from spring to summer. Our results show that Rhododendron+ O-horizon removal stimulates microbial activity by increasing soil C and N availability andsuggest that Rhododendroncanopy combined with O-horizon removal will alter soil C cycling by increasing microbial demand for soil C resources.

 

A modeling-monitoring approach to relate sediment loads to stream habitat quality and agricultural best management practices in Copper Creek (Clinch River)

Authors: Zachary P. Martin 1 and Paul L. Angermeier 1,2

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. U.S. Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Sediment pollution is a common driver of stream impairment and aquatic species imperilment. Although sediment dynamics and their connections to shifts in species distribution and habitat quality are poorly understood, stakeholders invest heavily in best management practices (BMPs) presumed to reduce sediment loading, improve water and habitat quality, and benefit aquatic biota. Copper Creek watershed (CCW) in the upper Tennessee River basin of Virginia illustrates the complexities of this issue in Central Appalachia. The stream hosts 12 imperiled aquatic species that rely on high-quality benthic habitats while the upland areas support a local economy dominated by agriculture. We address two main questions about CCW: (1) How does upland sediment load relate to benthic habitat conditions? and (2) Are agricultural BMP investments positively related to benthic habitat conditions? Ultimately, we will link a) sediment load estimates from a CCW model, b) our field data on physical habitat throughout CCW, and c) public data on BMP implementation in CCW to create stream network models of benthic habitat conditions. To date, we have generated sediment load estimates and collected habitat data from 78 study reaches, covering >11 fluvial km. Preliminary analyses suggest several benthic habitat metrics (e.g. D50, D35, % substrate as silt/clay, % embeddedness) are responsive to subwatershed-scale sediment loads and BMP metrics. However, some correlations suggest counter-intuitive relationships (e.g. poor habitat in subwatersheds with high BMP investment) and much variance in habitat quality is not explained by BMP metrics. Overall, our analysis suggests several tactics that may improve BMP cost-effectiveness.

The influence of social behavior and stability on disease transmission in a songbird host 

Authors: Matt Aberle 1, Jim Adelman 1, Dana Hawley 1

Affiliations: 1. Biological Sciences, Virginia Tech 

Human wildlife provisioning has long been overlooked as a major ecological factor, but in the last ten years it has been shown to be an important factor on the social behavior and physiology of wildlife and, consequently, disease. A prime example is among house finches (Haemorhous mexicanus) who, since the mid-1990s, have been subject to infection with a highly contagious bacterium, Mycoplasma gallisepticum, which causes debilitating conjunctival pathology. House finches congregate at bird feeders in social flocks, where most transmission takes place, making it an ideal system for testing hypotheses regarding how human provisioning influences social behavior, physiology, and disease transmission. To test the impact of bird feeders, I altered feeder density across several sites on the Virginia Tech campus while using radio-frequency identification to track social networks and individual behavior. By altering the density of feeders, my results show the effects of human feeding via bird feeders on this disease system by seeing changes in the social networks of house finches, individual behavior and physiology, and the prevalence of disease. 

 

Assessing local adaptation and physiological plasticity of a montane lizard in a warming climate

Authors: Brooke L. Bodensteiner 1 and Eric J. Gangloff 2

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. Station d’Ecologie Théorique et Expérimentale du CNRS Moulis, France

Determining how organisms will be impacted by a warming world is one of the most pressing scientific imperatives of the 21stcentury. Habitat tracking – species’ range shifts to more suitable habitat – is perhaps the most commonly observed response to rising temperatures. Terrestrial species are clearly moving upward in elevation and poleward in latitude. Nonetheless, there is a key asymmetry in habitat tracking, with species’ shifts to higher elevations occurring much more slowly than shifts to higher latitude. The mechanism for this asymmetry, however, remains predominantly unexplored. We do know that that species-specific physiological thresholds, relating to climate, set species’ distributions. For example, tracking suitable temperatures at higher elevations comes with the additional physiological challenge of contending with progressively limited oxygen concentrations. The goal of this project is to empirically test how oxygen availability across elevation may be limiting upslope migrations in a widespread terrestrial vertebrate the Common Wall Lizard (Podarcis muralis). I hypothesize that local temperature regimes and oxygen availability will interact to shape physiological traits, and the plasticity of these traits, in lizard populations from differ thermal regimes and levels of oxygen availability. By elucidating these interwoven factors, we can gain a more holistic understanding of the constraints organisms will encounter as they are faced with environmental warming.

 

Ailanthus Biocontrol

Authors: Rachel K Brooks 1, Scott Salom 2, Anton Baudoin 1

Affiliations: 1. Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic and State University, Blacksburg, VA  2. Department of Entomology, Virginia Polytechnic and State University, Blacksburg, VA

Ailanthus altissima (tree-of-heaven) is an invasive Chinese tree that has taken over portions of the Virginia landscape. Current control tactics are limited to expensive chemical and mechanical methods, and are impractical over large areas. Recently, two species of Verticillium fungi have been found naturally killing Ailanthus in Virginia. A statewide field inoculation study is underway to determine (1) if either of these isolates can be used as an effective biological control agent in the state, and (2) if any climate or stand variables impact Verticillium’s effectiveness. Preliminary results from the first field season indicate that V. nonalfalfae, alone or in combination with V. dahliae, cause significantly higher disease ratings than just V. dahliae or a control treatment. Additionally, disease progression was significantly influenced by two stand and climate variables: maximum temperature and tree height.

 

Examining the role of dispersal pathways in structuring aquatic insect communities

Authors: Sara Cathey 1 and Bryan L. Brown 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia

Aquatic insects use different pathways to disperse between communities. This heterogeneity in dispersal behavior may affect how communities of stream macroinvertebrates are structured and how variable insect assemblages are over time. For my dissertation, I will investigate what role different dispersal pathways play in the assembly of aquatic macroinvertebrate communities in a stream network and how this dispersal-driven assembly changes with position in the network. I will also investigate how this dispersal-driven community assembly affects the stability of stream macroinvertebrate communities, taking into account both the taxonomic and trait composition of stream macroinvertebrate communities. I predict that isolated headwater communities are structured more by aerial dispersal, while mainstem communities located at nodes in the network are structured more by drift dispersal. The influence of drift dispersal from the headwaters that structures mainstem communities will diminish with an increase in the stream order of the mainstem. I predict community stability will be lowest in headwater assemblages and highest in the mainstem sites. These studies will help elucidate how different dispersal routes structure communities and stabilize communities. Determining how dispersal drives community assembly may give us insight into how these communities respond to disturbance, habitat fragmentation, and biological invasion. Understanding the assembly of aquatic insect communities may also inform conservation and restoration strategies.

 

Base cations as drivers of bacterial water quality impairment

Authors: Stephen DeVilbiss 1, Meredith Steele 1, Brian Badgley 1

Affiliations: 1. Department of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg, VA

Base cations (Ca, Mg, K, Na) are common constituents of both terrestrial and aquatic environments. However, human activities including agriculture, deicing, surface mining, and construction have resulted in increasing ion concentrations in North American surface waters. While it is well established that the total inorganic ion concentration, or salinity, significantly impacts aquatic bacteria, the effects of individual base cations on bacterial ecology are unknown. Further, most studies focus on broad salinity ranges from freshwater to marine, and fail to address small scale changes in ion concentrations. As freshwaters continue to become saltier from manageable anthropogenic activity, small increases in salts (<50 mg/L or 350 μS/cm), as well as the types of salts causing those increases, may become increasingly important drivers of ecosystem health.We have previously identified strong correlations between base cations and the fecal indicator bacterium E. coliin watersheds in Southwestern Virginia. However, mechanisms driving these correlations in the environment have yet to be experimentally tested and remain a substantive knowledge gap. Here, we test the effect of elevated concentrations of individual base cations on the survivability of E. coliin controlled mesocosm experiments. Results suggest that divalent base cations, Ca and Mg, significantly increase the survivability of E.colirelative to K treatments and controls with no salt additions. These results suggest that elevated concentrations of divalent base cations may increase bacterial impairments in surface waters.

 

Does the microbiome impact reintroduction success of captive species? A test with an endangered frog

Authors: Angie Estrada 1, Daniel Medina 1, Brian Gratwicke 2, Roberto Ibanez 3, Lisa K. Belden 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech  2. Smithsonian’s National Zoo & Conservation Biology Institute  3. Smithsonian Tropical Research Institute, Panama.

Beneficial skin bacteria can protect amphibians against Batrachochytrium dendrobatidis(Bd), a deadly pathogenic fungus that is one of the largest threats to amphibian survival worldwide. For many amphibian species, long-term captive breeding programs have prevented extinction; however, captive management is known to modify the amphibian skin microbiome. In Panamá, threatened amphibian species survive in captive breeding facilities, but have only recently been experimentally reintroduced into the wild. For tropical amphibians, it is unknown how skin bacterial community diversity and structure change once captive-bred individuals are re-exposed to natural habitats. Thus, to inform the development of beneficial bacteria-based treatments, and also future reintroduction efforts, we attempted to understand amphibian-Bd-skin bacterial community interactions in reintroduced captive-bred individuals. Specifically, we assessed the changes that occur in the bacterial communities of Atelopus limosus, a critically-endangered species, following reintroduction to a site where the species historically occurred. We aimed to investigate how the initial skin bacterial community influences: 1) bacterial community structure and composition after release, 2) host condition and 3)Bdinfection status. Relative abundance of bacterial OTUs (operational taxonomic units, ~bacterial species) based on 16S rRNA gene amplicon sequencing was used to assess skin bacterial community diversity. We found significant variation in bacterial community structure before and after release.  In addition, we found variation in bacterial community structure through time once exposure to natural conditions occurred. Moreover, after only two weeks, reintroduced and wild individuals had more similar skin microbiomes. These preliminary findings suggest that skin-associated microbiomes can be restored once captive-bred individuals are re-exposed to natural habitats, but future research needs to address whether these changes in bacterial structure ultimately result in higher survival and Bd protection of captive-bred amphibians.

 

Connecting long-term data with fine-scale variation: using remote sensing to evaluate spatiotemporal dynamics of drylands ponds

Authors: Mary Jade Farruggia 1, Meghan Halabisky 2, Meryl C. Mims 1

Affiliations: 1. Virginia Tech – Department of Biological Sciences  2. University of Washington and Conservation Science Partners

Hydroperiod is a major driver of aquatic communities in lentic systems and may be particularly relevant in areas where water availability is a major limiting factor. In the American Southwest, water availability is threatened by unsustainable water use and increased drought. There, manmade lentic habitats such as cattle ponds may provide critical habitat for aquatic organisms when natural systems are lost. However, spatial distribution and hydroperiod dynamics of manmade ponds in this region are poorly understood, representing a knowledge gap about spatiotemporal availability of lentic habitat. To address this, we asked: (1) How are manmade ponds spatially distributed in this region? (2) Which ponds are permanent, and which are intermittent? (3) What are the ponds’ hydroperiods, and do they change over time? We will use graph theory and spectral mixture analysis to analyze 34 consecutive years (1983-2017) of satellite imagery in Coronado National Forest, Arizona, to characterize the spatial distribution of ponds on the landscape, estimate surface water, and classify hydroperiods across multiple time scales. As global change progresses, understanding regional water availability is increasingly important for contextualizing aquatic community stability and optimizing management to promote persistence of native aquatic organisms.

 

Evidence of an adaptive trade-off in a weedy, invasive grass grown near the edge of its distribution

Authors: Rebecca A. Fletcher 1, Daniel Z. Atwater 1,2, David C. Haak 1, Jacob N. Barney 1

Affiliations: 1. Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia  2. Department of Biology, Earlham College, Richmond, Indiana

The rapid range expansion of some exotic invasive plants is thought to be facilitated by their ability to quickly adapt to the novel environmental conditions they experience in their new ranges. However, fitness trade-offs may constrain adaptation, especially at the geographic range periphery where genetic diversity may be low, thereby, restricting further range expansion. One important fitness trade-off is that of earlier flowering time. Flowering earlier has been found in plant populations growing near the periphery of their distributions. Life history theory predicts that plants that flower early will be smaller in size, which results in decreased reproductive output. We used the globally distributed, invasive plant Johnsongrass (Sorghum halepense) to determine whether populations originating from the range periphery (where Johnsongrass is rare) exhibit characteristics consistent with the adaptive trade-off between flowering time and reproductive output. We collected populations of Johnsongrass from the center, edge, and periphery of its distribution and grew them in a common garden experiment located near Blacksburg, VA. We found the periphery populations were half the size of the other populations and flowered 10 days earlier, but we did not find evidence of reduced reproductive output in the periphery populations. This suggests that there is a trade-off between flowering time and investment in growth, but this trade-off did not seem to affect the reproductive output of Johnsongrass. Further studies are needed to determine why Johnsongrass has not successfully colonized regions beyond the edge of its distribution.

 

 

Evolutionary mechanisms of toxin resistance in snakes and lizards

Authors: Kerry L. Gendreau 1, Angela D. Hornsby 1, Joel W. McGlothlin 1

Affiliations: 1. Biological Sciences, Virginia Tech, Blacksburg, VA

Parallelism describes convergent evolution using a shared mechanism and can occur at multiple scales (i.e. at the molecular, phenotypic, and/or ecological levels). Convergent evolution of toxin resistance in snake species is a well-characterized example of molecular parallelism. Tetrodotoxin (TTX), used as a chemical defense by some fish and amphibian species, causes paralysis by targeting vertebrate sodium channel proteins necessary for the propagation of action potentials in muscles. Nine types of sodium channel proteins are present in vertebrates, each with different kinetic properties and levels of tissue expression. Substitutions in a functionally conserved region of the sodium channel gene expressed in skeletal muscle (SCN4A) provide some snakes with resistance to high levels of TTX, and have evolved convergently in distantly related species that consume toxic amphibian prey. Resistance to TTX in SCN4A appears to have evolved over a relatively short timespan in snakes experiencing strong selective pressure from consuming toxic amphibians. In contrast, sodium channels expressed in heart muscle and sensory neurons acquired resistance before the split of the last common ancestor of snakes and lizards, and may be necessary to drive selection on skeletal muscle channels. Using the genome sequences of species representing major phylogenetic branches of the order Squamata(snakes and lizards) as well as the tuatara,we will gain insight into the evolutionary history of the entire voltage gated sodium channel gene family. This will shed light on the amount and scale of parallelism in this gene family and the mechanisms controlling convergent evolution under conflicting selective pressure.

 

Microbiome mediated plant-pollinator interactions

Authors: Ariel Heminger 1, David C. Haak 1,

Affiliations: 1. Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic and State University, Blacksburg, VA

Plants and their pollinators depend heavily on the synergy of one another. The majority of flowering plants require pollinators to ensure the spread of pollenand pollinators often depend on plants for pollen and nectar as a food source. In agriculture alone native pollinators contribute between $4.1 to $6.7 billion dollars annually. Woven into this relationship are microorganisms that form close relationships with their hosts forming the microbiome. The microbiome is intricately associated with the organismal health through processes such as nutrient acquisition and disease suppression. Recent studies have found that pollinators exchange microbes with the flowers they pollinate—leaving a microbial fingerprint. This suggests that flowers and their pollinators could have reciprocal influences on their associated microbes that have been shaped over evolutionary time.  However, few studies have examined the impact of this reciprocal interaction on microbial community structure, eco-evolutionary dynamics, or plant health. This study aims to fill this gap through three specific objectives:  1) characterizing the floral and pollinator microbiome across several natural populations of Solanum carolinenseand its pollinator Bombus spp., 2) examining the same traits in populations (paired with 1) of a congener Solanum dulcamarathat was introduced less than 200 years ago, and 3) investigating the impact of the pollen microbiome on seed endophytic communities.By focusing on the microbial interactions between a native plant species Solanum carolinense, horsenettle, and an introduced species Solanum dulcamara, bittersweet nightshade and their pollinators, Bombus spp. in Virginia. This study will contribute to the body of knowledge on plant-pollinator interactions at the microbial level and help further determine how the microbiome is linked to plant and pollinator health.

 

Chemical defense gland evolution in a millipede Müllerian mimicry ring

Authors: Derek A. Hennen 1, Paul. E Marek 1

Affiliations: 1 Department of Entomology, Virginia Polytechnic Institute & State University, Blacksburg, VA

Apheloriine millipedes are common detritivores found in the undergrowth of Appalachian temperate forests. They exhibit an array of bold color patterns, which function as aposematic signals advertising their unpalatability to potential predators such as birds. The toxicity of these millipedes is due to their paired, bi-compartmental chemical defense glands, which produce a poisonous mix of hydrogen cyanide and benzaldehyde at levels sufficient to kill 18 pigeon-sized birds. Shared chemical defenses and color patterns have been noted in the group before, and a Müllerian mimicry ring among seven species in three different genera (Apheloria, Appalachioria, and Brachoria) has recently been documented in the Cumberland Mountain Thrust Block Region of Virginia, Tennessee, and Kentucky. In this mimicry ring, Apheloria was hypothesized to be the more toxic model, with Appalachioria and Brachoria mimicking Apheloria color patterns. However, the hypothesis of Apheloria as the model in this mimicry ring has not been directly tested. To investigate this question, we compared the size of the chemical defense glands in sympatric populations of the genera Apheloria and Brachoria as a proxy for toxicity. We found that the chemical defense glands of Apheloria were significantly larger than those in Brachoria, supporting the hypothesis that Apheloria acts as the more toxic model in the mimicry ring.

 

Sexually transmitted pathogenic bacteria as a cost of extra-pair activity to female birds

Authors: Jessica Hernandez 1,

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute & State University, Blacksburg, VA

Important questions in evolutionary and organismal biology often center around the trade-offs of different mating strategies. Up until the 1980s, most bird species were considered to be truly monogamous, or sexually faithful to a social partner. However, with recent molecular advances, the evidence suggests quite the opposite pattern: nearly 90% of bird species engage in fertile copulations outside of the social pair (i.e., extra-pair fertilizations). Sexually transmitted diseases have been suggested to be a cost of extra-pair fertilizations in birds for the past four decades, but has not yet been adequately tested.This research focuses on a local population of box-nesting tree swallows (Tachycineta bicolor), a species in which individuals have been shown to be socially monogamous, yet also engage in high rates of extra-pair fertilizations. We collected cloacal samples from adult male and female tree swallows during the 2016 breeding season, and subsequently extracted, amplified, and sequenced the bacterial DNA from those cloacal samples. Here, we present preliminary data that we used to answer the question: What is the relationship between the cloacal bacterial communities of males and females, in general, and of social pairs? With regard to cloacal bacterial communities, we found that 1) there is variation within sexes and 2) social pairs were not more similar compared to other sampled individuals in the same population. Our next step is to assess the relationship between cloacal bacterial communities and rates of extra-pair fertilizations. Ultimately, we hope to shed some light on the relationship between extra-pair fertilizations and the presence, prevalence, and potential pathogenicity of sexually transmitted microbes, with respect to fitness, in a wild avian population.

 

Implications of a changing climate on bird development

Authors: Sydney F. Hope 1, Sarah E. DuRant 2, Robert A. Kennamer 3, William A. Hopkins 1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Tech 2. Department of Integrative Biology, Oklahoma State University 3. Savannah River Ecology Lab, University of Georgia

Our changing climate may pose a threat to the early developmental environment of animals. The effect of climate change on developing reptiles is well-studied, and there is evidence that changes in incubation temperature can have substantial effects on offspring. In contrast, the effects of temperature changes on bird phenotypes have been historically overlooked because parents regulate incubation temperature. However, studies have shown that changes in the environment can affect avian parental incubation behavior, and that small changes in incubation temperature can affect avian offspring phenotypes. Yet, few studies have investigated how environmental changes may directly and indirectly influence incubation temperature, and no studies have investigated how incubation temperature influences avian offspring behavior. We used wood ducks as a model system to address these questions. Our results show that wood duck nests with the largest clutch sizes and the lowest ambient temperatures led to the lowest incubation temperatures. We also found that ducklings incubated at 35 and 37°C exhibited bolder and more exploratory behaviors than those incubated at 35.8°C, while those incubated at 35°C were less successful at exiting the nest (a crucial behavior for wood duck ducklings) than those incubated at the other two temperatures. This research shows that environmental changes influence avian incubation temperature and thus, may influence offspring behaviors that are critical for survival. In this case, warming temperatures may be beneficial to developing birds, but future work should address how extreme weather events or changes in food availability due to climate change affect incubation temperature.

 

Mapping Climate Envelopes to Hypothesize Ecotypic Variation of an Invasive Plant

Authors: Vasily Lakoba 1 and Jacob Barney 1

Affiliations: 1. Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Invasive plants cause an estimated 35 billion dollars in damage and control costs in the United States annually (Pimentel et al., 2005). Johnsongrass (Sorghum halepensePers., Poaceae) is a global invasive species with a prominent range in the southern half of the continental United States. Over its 190-year invasion history in the U.S., it has shown a directional transition from agricultural to non-agricultural habitats (Sezen et al., 2016). Recently, agricultural and non-agricultural lineages were found to respond divergently to climate variables (Atwater et al., 2016). By studying human land uses as drivers of ecotypic divergence, we can begin to predict invader spread and physiology in the landscape with greater sensitivity.

In this project, U.S. Johnsongrass observations 1981-2018 from the Global Biodiversity Information Facility (GBIF) and the Early Detection and Distribution Mapping System (EDDMapS) were used to sample PRISM climate norm data for 1981-2010. The observations were then subset based on human land uses and the resulting climate envelopes were projected on the continental United States. This method found divergent climate envelopes based on temporal, (non)agricultural, land-use-change, and impervious surface subsetting. It also found three distinct cores within the range, which had previously been considered as largely an east-west dichotomy.

Geospatial evidence supports the connection between human land uses and Johnsongrass climate responses. These GIS analyses are a rationale for locating range cores with the highest likelihood of ecotypic variation for in-situ measurement of soil and plant community predictors of divergent adaptation.

 

Urbanization impacts nestling corticosterone but not offspring growth in song sparrows

Authors: Lane, S. 1, Sewall, K. 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg VA

Urbanization represents a dramatic and relatively rapid change in environment, which animals may cope with through phenotypic plasticity. In previous studies, it has been shown that male song sparrows (Melospiza melodia) in urban habitats show higher levels of territorial aggression than their rural counterparts. Such differences in male behavior could have consequences for offspring, as territorial aggression can be traded off against paternal care. Therefore, we compared nestling growth, corticosterone (CORT) levels, and survival among three rural populations (N = 15 nests/30 nestlings) and two urban populations (N=19 nests/45 nestlings) of song sparrows near Blacksburg, VA. We found that nest predation was higher in rural habitats, based on evidence of disturbance at the nest site. Additionally, we found that nestling baseline CORT levels were significantly higher in rural habitats, though there were no differences in overall nestling growth rates. Finally, there was a non-significant trend towards increased nest parasitism by brown-headed cowbirds in urban habitats. These findings suggest that male territorial aggression does have consequences for offspring CORT levels. Additionally, these findings suggest that there are differences in relative risks of predation and nest parasitism across rural and urban habitats, which could potentially drive variation in male territorial aggression.

 

Whole-ecosystem experiments reveal differential responses of phytoplankton functional groups to epilimnetic mixing

Authors: Mary Lofton 1, Ryan McClure 1, Shengyang Chen 2, John Little 3, Cayelan Carey 1

Affiliations: 1. Biological Sciences, Virginia Tech 2. Civil Engineering, University of Sydney 3. Civil & Environmental Engineering, Virginia Tech

Phytoplankton blooms are increasing in lakes and reservoirs worldwide, causing detrimental effects on drinking water quality. One management strategy for controlling phytoplankton is epilimnetic mixing systems, intended to decrease surface scums by increasing water column turbulence. However, past work has demonstrated that the efficacy of epilimnetic mixing for decreasing phytoplankton biomass is equivocal. This may be because phytoplankton community responses to epilimnetic mixing are mediated by mixing effects on other ecosystem processes, such as nutrient dynamics and thermal stratification, and quick-sinking phytoplankton taxa may benefit from a well-mixed water column. To assess effects of epilimnetic mixing at the whole-ecosystem scale, we conducted two mixing experiments in a drinking water reservoir. We measured a suite of physical, chemical, and biological variables before, during, and after mixing and compared the results to a nearby, unmixed reference reservoir. We found that phytoplankton biomass, especially cyanobacteria, green algae, and cryptophytes, significantly increased after our first mixing event due to an increase of nutrients, likely from entrainment of sediments into the epilimnion. Total phytoplankton biomass did not significantly change after our second mixing event; however, phytoplankton community composition after the second mixing event exhibited a shift from taxa with filamentous morphology to smaller, rounder taxa. Our results suggest that phytoplankton responses to epilimnetic mixing are intertwined with turbidity and nutrient dynamics, and that these responses may vary depending on the timing of mixing and morphology of phytoplankton taxa. Whole-ecosystem dynamics and functional traits should be considered when managing phytoplankton biomass by epilimnetic mixing.

 

Disparate drinking water quality and compliance across urban and rural Virginia under the Safe Drinking Water Act

Authors: Cristina E. Marcillo 1 and Leigh-Anne Krometis 1

Affiliations: 1. Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Approximately 299 million Americans receive household drinking water from one of 51,350 community water systems (CWSs) under the Safe Drinking Water Act (SDWA). Despite a history of amendments and financial investment, repeated violations and noncompliance persists. This study hypothesizes that community exposures to drinking water contaminants are significantly different between rural and urban US communities. The goal was to analyze historic SDWA violations in Virginia to 1) understand the relationships between system size, rurality, and compliance and 2) evaluate the most prevalent drinking water contaminants.

Violation data from 1999-2016 for 1,135 Virginia CWSs were analyzed (n>9500 violations, source: Safe Drinking Water Information System). Systems were geocoded in ArcGIS, with the US Department of Agriculture’s Rural-Urban Commuting Area (RUCA) codes defining rurality at the zip code level. As would be expected, small systems serving less than 3,300 people each had 64% of all health-based violations across the state while very large systems serving more than 100,000 people each had 0.07% of all health-based violations. Analyses of geocoded CWSs (n=671) indicated that rurality had a significant effect on total (Kruskal-Wallis, χ2=22.39, p<0.01) and monitoring and reporting violations (χ2= 28.03, p<0.001). Additionally, both health based and monitoring and reporting violations were significantly different between differently sized systems.

Confirmation that SDWA compliance differs by rurality suggests that rural communities may be more likely to be exposed to drinking water contaminants of health concern. Ongoing efforts will expand this analysis to include the influence of community demographics (e.g. race, % foreign born) on SDWA compliance.

 

Why do birds of different feathers flock together? A case study on a cooperatively breeding habitat specialist

Authors: Noah McNeill 1, Dr. Jeff Walters 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech University, Blacksburg, Virginia, USA

Birds are known to form flocks in numerous systems, many of which are mixed-species flocks. Individuals may choose to mixed-flock in order to increase foraging efficiency, limit intraspecific competition, or reduce predation. In the longleaf pine system, brown-headed nuthatch (Sitta pusilla) join mixed flocks during the nonbreeding season, but are subject to variable predator presence and food availability. I plan to record mixed-flocking rates of brown-headed nuthatch, as well as predator interactions at Marine Corps Base Camp Lejeune. Nuthatches will be color banded and surveyed using a combination of scan and focal sampling. Additionally, I will experimentally manipulate food availability by placing feeding stations in portions of the field site. I will then record station usage rates and flocking behavior surrounding these stations. I expect that tendency to join mixed flocks is inversely correlated to pine seed availability and individual territory quality. Alternatively, I expect mixed flocking to positively correlate with predator presence, particularly during the winter influx of migrant predators. Determining how these factors impact nonbreeding nuthatch behavior will inform population management strategies for improved winter survival.

 

Diversity and symbiosis: Examining the taxonomic, genetic, and functional diversity of amphibian skin microbiota

Authors: Myra Hughey 1, Matthew Becker 1, Tiffany Bridges 2, Brian Gratwicke 3, Reid Harris 2, Leanna House 4, Roberto Ibanez 3, Roderick Jensen 1, Stephen Loftus 4, Daniel Medina 1, Kevin Minbiole 5, Eria Rebollar 2, Thomas Umile 5, Jenifer Walke 1, Lisa Belden 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech  2. Biology Department, James Madison University  3. Smithsonian Institution & Panama Amphibian Rescue and Conservation Project  4. Department of Statistics, Virginia Tech  5. Chemistry Department, Villanova University

For decades ecologists have contemplated the potential consequences of biodiversity loss, which has resulted in a rich literature searching for links between biodiversity and ecosystem function. Within this context, our research has aimed to understand the link between diversity and function by investigating the amphibian skin bacterial communities and their role in controlling the disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis(Bd).  Chytridiomycosis is decimating many amphibian populations in the Neotropics. Thus, our work has focused on investigating the link between bacterial community structure and function in Panamanian amphibians. We conducted a field survey to examined six host species that vary in Bd susceptibility at a Bd naïve site, and a second survey to examine three non-susceptible host species across sites that varied in timing of Bd arrival. Bacterial community structure was assessed using 16S rRNA gene amplicon sequencing, and their potential function was assessed by using HPLC-MS to produce profiles of secondary metabolites. In addition, we also assessed inhibition of Bd growth by bacterial isolates cultured from these skin communities. Overall, we found host species-specific skin bacterial communities, and that these communities may vary among populations of the same species across sites. In addition, host species that are more susceptible to Bd differed in their skin bacterial communities from more resistant species. Moreover, the arrival of Bd at a site may result in shifts in bacterial community structure. However, metabolite profiles across species were not always distinct, suggesting that similar functions might result from different bacterial community structures.

 

Resource Use and Interspecific Interactions in a Namibian Cavity-nesting Community

Authors: David Millican 1, Jeff Walters 1, Ashley Dayer 2

Affiliations: 1. Department of Biological Sciences, Virginia Tech, 2. Department of Fish and Wildlife Conservation, Virginia Tech

Cavity-nesting guilds are diverse communities of vertebrates and invertebrates found in forest ecosystems worldwide. Due to their dependence on tree holes for nesting, species in these communities are limited by an availability of suitable nest cavities. This dependence therefore leaves these species susceptible to forms of disturbance that diminish cavity availability, such as anthropogenic forest management, stochastic events, and climatic shifts. Namibia is the driest country in sub-Saharan Africa, with a landscape largely depauperate of large trees, the most common harborers of cavities. This community is threatened by numerous anthropogenic disturbances, including charcoal production, altered grazing and fire regimes, and increasingly frequent and severe droughts caused by climate change. To aid the conservation of this threatened community, we have embarked on a multi-year nest-web analysis to quantify community structure. Through this analysis, we will seek to describe the type and structure of available nest cavities, species-specific resource use preferences, and direct and indirect interactions between community members. By quantifying community structure, we willprovide important information for land use managers to mitigate the impacts of anthropogenic disturbance on this community. We have also coupled our ecological research with a human dimensions study on wildlife perceptions of local communities. Using focus-group interviews, we are using emotional prompts as a way to identify a potential flagship species. By combining ecological and sociological research, we hope to generate both ecological management plans for conserving this community as well as sociological strategies to generate local support for a conservation campaign.

 

Time budgets of juvenile male Red-cockaded Woodpeckers before dispersal

Authors: Leah D. Novak 1, Jeffrey R. Walters 1, Dylan Kesler 2

Affiliations: 1. Biological Sciences, Virginia Tech 2. The Institute for Bird Populations

Natal dispersal is the movement of individual animals from a birth site to a breeding site.  Often, before dispersal, juveniles explore outside their natal territory to gather information from the environment and conspecifics regarding habitats and conditions.  Understanding the behavior of these individuals while they explore is key for understanding and predicting how a species interprets and interacts with the biotic and abiotic landscape, and is especially important for creating and implementing effective management strategies especially for endangered species, such as the Red-cockaded Woodpecker (RCW).  The cooperatively breeding RCW is a federally listed endangered species endemic to open, southern pine savannah in the Atlantic and Gulf Coastal Plains of the United States.  Male RCWs have two dispersal syndromes: they can either delay dispersal and remain on their natal territory as non-breeding helpers, or disperse their first year in search of territories with open breeder positions.  Dominance within broods plays an important role in determining which dispersal strategy a juvenile male will use.  Dominant males almost always remain as helpers, while subordinates disperse their first year.  Despite understanding dispersal outcomes of male and female RCWs, very little is known about the males behave during dispersal.  Therefore, I followed dominant and subordinate juvenile males using radio-telemetry and made behavioral observations to determine the time budgets of these individuals.  I found that subordinate and dominant juvenile males both forayed extensively. Juveniles spent most of their time foraging while foraying, especially in the morning, although dominant males tended to spend more time traveling than subordinate males.  Also, subordinate juveniles spent time exploring cavities in other RCW territories, which dominant males did not.

 

Representing forest management in Earth System Models

Authors: Joshua M. Rady 1, R. Quinn Thomas 1

Affiliations: 1. Department of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University

As the major terrestrial carbon sink forests are seen as a critical tool to help combat climate change.  A quarter of the emissions reductions pledged in the Paris Climate Accords come from preservation and expansion of forests.  Given the stakes it is critically important that we make wise choices in employing these mitigation approaches.  In this context forest management techniques developed to increase timber production might be usefully repurposed to increase carbon sequestration.  Forests both influence and are influenced by climate.  Therefore, fully coupled Earth System Models (ESMs) must be used to fully understand the effects of the mitigation approaches that employ forests.  Currently ESMs simulate forest management in a rudimentary manner.  Some important management activities, like harvest rotation and fertilization, are not represented at all.  We have completed the initial steps to incorporate these management activities into the Community Land Model, the terrestrial component of NCAR’s CESM Earth System Model.  We have altered the hierarchical representation of vegetation on the model’s gridded land surface.  This allows us to isolate portions of forest in a grid cell for management activities.  In initial experiments, we have demonstrated the isolation of wood harvest onto a specified segment of forest, where previously it occurred everywhere.  This lays the groundwork for increasingly relevant activities such as fertilization, fire exclusion, harvest rotations, as well as representing protected forest areas.  We hope these improvements will increase the value of these models to decision makers in the climate policy arena.

 

Population trends in northern Madagascar’s endangered and critically endangered lemurs: Should we be concerned?

Authors: Brandon P. Semel 1, Sarah M. Karpanty 1, François Angelo Andrianiaina 2, Katherine A. Lipford 1, Dimbison Vévé Rasolomanana 3

Affiliations: 1. Department of Fish & Wildlife Conservation, Virginia Tech, Blacksburg VA  2. Department of Animal Conservation & Biology, University of Antananarivo, Madagascar  3. Department of Life Sciences & the Environment, University of Mahajanga, Madagascar

Habitat loss, hunting, and climate change continue to threaten Madagascar’s lemurs. Despite the rapid creation of protected areas during the first part of the century, we still know precious little about lemur populations across the island. Three diurnal lemur species can be found across less than 440 km2of fragmented forests within the Loky-Manambato Protected Area. Critically endangered golden-crowned sifakas (Propithecus tattersalli) are endemic to the region and have been the focus of several studies across the protected area. Little is known about endangered crowned (Eulemur coronatus) and Sanford’s brown (E. sanfordi) lemurs in the region. Standard line transects were used to survey these and other vertebrate species in a total of nine fragments from 2016-2017. Species densities and abundance were determined using the “Distance” package in Program R. Population estimates suggest a decline in sifaka populations since 2006/2008. However, local taboos seem to continue to protect this species form hunting. Here, we present the first estimates of crowned and Sanford’s brown lemurs in the region. Evidence of continued forest loss, disturbance, and hunting of the two Eulemur species was found across all survey areas, even those that were conducted in strict conservation zones (noyaux durs). We suggest that increased patrols of conservation areas be conducted to prevent continued biodiversity loss in the protected area.

Material based upon work supported by the NSF GRFP (No. DGE 1607310). Opinions, findings, conclusions, or recommendations expressed are thoseof the authors and do not necessarily reflect the views of the NSF.

 

Exploring group cohesion and social proximity in golden-crowned sifakas

Authors: Meredith Semel 1, Yasmireilda Richards 2, Nicole Abaid 3, and Ignacio Moore 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia  2. Department of Animal Biology and Conservation, University of Antananarivo, Madagascar 3. Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, Virginia

Traditionally, studies examining group cohesion in primates have taken a “boots and binoculars” approach. While observational data is effective in understanding primate social behavior, it is challenging and the data are limited by the amount of time the investigator can spend monitoring the troop. Commercially available tracking equipment is promising but their application limited due to high cost. To address this issue, we have designed a modular, open-source tracking collar, FitPET (“FITness, Proximity, Energetics, and Tracking”), that is capable of collecting data on primate cohesionandcan provide truly innovative insights into how habitat structure and fragmentation influence group cohesion. To determine how primate social cohesion is impacted by landscape type and to ground-proof the use of our devices, we completed 7 full-day behavioral follows for eleven groups of golden-crowned sifakas (Propithecus tattersalli) in an array of rainforest and dry forest fragments surrounding Daraina, Madagascar (August-December 2017). Using scans at ten-minute intervals, we recorded activity, height, feeding information, nearest neighbor proximity, and group spread. Group spread was determined by measuring the distance between the farthest two individuals in each group. Overall, we observed a relationship between fragment type and group spread; with sifakas displaying decreased group cohesion in rainforest fragments. Now that we have an understanding of how P. tattersallisocial cohesion differs between fragment types, we willbe employing the use of our FitPET devices to automate our data collection and more effectively collect data on spatial dynamics and social interactions of sifaka groups.

 

Land use versus climate drivers of algal production in an oligotrophic lake: it depends on season

Authors: Nicole K. Ward 1, Bethel Steele 2, Kathleen C. Weathers 2, Kathryn L. Nottingham 3, Holly A. Ewing 4, Paul C. Hanson 5, Robert Wood 6, June Fitcher 6, Cayelan C. Carey 1


Affiliations: 1. Biological Sciences, Virginia Tech  2. Cary Institute of Ecosystem Studies 3. Biological Sciences, Dartmouth College  4. Program in Environmental Studies, Bates College  5. Center for Limnology, University of Wisconsin-Madison  6. Lake Sunapee Protective Association

Globally, lake water quality is decreasing as a result of global warming and excess nutrient loading from land use change (e.g. clearing of forests). Clear-water, or oligotrophic, lakes are particularly vulnerable to changes in water quality; they can “flip” to a low-water quality state through the essentially irreversible process of eutrophication. To work toward maintaining oligotrophic lakes and the highly valuable ecosystem services they provide (e.g. drinking water and recreation), managers and scientists need to understand the relative contribution of land use and climate drivers to water quality change. Here, we address the question, how is land use and climate affecting water quality in an oligotrophic lake over 3 decades? Our study site is Lake Sunapee, which is the 3rdlargest lake in New Hampshire. The lake experiences variable annual phosphorus loading, precipitation, and air temperature. Average annual air temperature is increasing at a rate of 0.04 °C per year (from 1979 to 2016;r2= 0.36). We calibrated and validated a 1-dimensional hydrodynamic model coupled with an aquatic ecosystem model to simulate lake dynamics over 3 decades. In analyzing each summer growing season, multiple linear regression analysis shows that summer (Jun-Jul-Aug) chlorophyll-a, a measure of algal production, is driven primarily by summer temperature (contributing to 91% of overall model fit), whereas fall (Sept) chlorophyll-a is driven primarily by spring (Mar-Apr-May) phosphorus loading (contributing to 83% of overall model fit). Unique drivers to algal production at different times of year have important implications for managing valuable oligotrophic lake ecosystems in the face of global warming and land use change.

 

Environmental dissemination of antibiotic resistance in dairy manure and compost-amended vegetable fields

Authors: Wind, L. 1, Hession W.C. 1, Krometis L.-A. 1, Chen C. 2, Du P. 3, Pruden A. 4

Affiliations: 1. Virginia Tech, Biological Systems Engineering, Blacksburg, United States  2. Virginia Tech, Crop and Soil Environmental Sciences, Blacksburg, United States  3. Virginia Tech, Statistics, Blacksburg, United States  4. Virginia Tech, Civil and Environmental Engineering, Blacksburg, United States

Increasing evidence links the widespread use of antibiotics in livestock production to the transfer of bacteria carrying antibiotic resistance genes (ARGs) to the broader environment. It is therefore critical to understand the persistence and mobility of both resistant microorganisms and associated genetic material in these systems in order to understand potential threats to consumers. We evaluated the effects of soil amendment type (inorganic fertilizer, raw dairy manure, composted dairy manure, or no amendment), vegetable type (lettuce, radish), and antibiotic use (pirlimycin and cephapirin) of cattle manure-derived amendments on the incidence of culturable antibiotic-resistant fecal coliforms through a field-scale controlled plot experiment. Antibiotic-resistant culturable fecal coliforms were recoverable from soils across all treatments immediately following application, though persistence throughout the experiment varied by antibiotic class and time. Compost-amended soils had the highest levels of cephalosporin-resistant fecal coliforms, regardless of the antibiotic history of the cows providing the manure. Significantly, higher levels of total, ceftazidime, and erythromycin-resistant fecal coliforms were recovered from compost-amended as compared to the raw manure-amended soils. Parallel quantification of resistance genes (sul1, tet(W), erm(B), intI1) was used to confirm observed culturable trends. Soils amended with raw dairy manure yielded high relative sul1 and tet(W) gene copies on Day 0, correlating with an observed spike in associated ARBs, and remained detectable for 113 and 39 days longer than resistant bacteria, respectively. Interestingly, erm(B) was not detected, despite detection of erythromycin-resistant bacteria in the soil and erm(B) in a parallel runoff study. This work is of particular interest given the relevance of fecal coliforms in tracking human pathogen risk in multiple environments (e.g., water, crops) throughout agricultural production.

Bridge in woods

2nd Annual

Interfaces of Global Change Graduate Student Research Symposium

April 21, 2017
Fralin Hall

The second annual Interfaces of Global Change (IGC) Graduate Research Symposium was held on April 21, 2017 in Fralin Hall. The symposium provided a forum for students and faculty to interact and explore connections between labs across campus. The day included 9 oral presentations, a poster session, and a keynote address by former U.S. Congressman, Bob Inglis.

The symposium highlighted the latest research from the program’s graduate student fellows, whose collective work addresses critical global changes impacting the environment and society. This includes problems surrounding climate change, pollution, invasive species, disease, and habitat loss.

Platform awards for Best Presentation were announced at the conclusion of the symposium. The winners included:

Tony Timpano receives the 2017 DePauw Award for Best Presentation


First Place Tony Timpano
, “Effects of coal mining on freshwater salinization and aquatic insect diversity”

Second Place Tamara Fetters, “Life histories and invasions: accelerated laying rate and incubation time in an invasive lizard, Anolis sagrei

Third Place Laura Schoenle, “Surviving or thriving with malaria: the role of stress hormones in mediating resistance and tolerance”

Congratulations to all the student participants!

See more photos from the Symposium on FLICKER

Detailed AGENDA PDF

Friday, April 21, 2017

8:30 a.m.         Poster setup; Fralin Hall Atrium

9:10 a.m.         Welcome (Jeff); Fralin Auditorium

9:15 a.m.         Session 1 (S1); Session Chair: Heather Govenor

9:15 a.m.         S1 Talk 1 Laura Schoenle

9:30 a.m.         S1 Talk 2 Tamara Fetters

9:45 a.m.         S1 Talk 3 Brandon Semel

10:00 a.m.       S1 Talk 4 Derek Hennen

10:15 a.m.       Premiere: Freshwaters in the Anthropocene (Science Communication Films; Cayelan Carey)

10:55 a.m.       Break

11:15 a.m.       Keynote Talk (Bob Inglis)

12:15 p.m.       Lunch and poster viewing; Fralin Atrium

1:15 p.m.         Session 2 (S2); Session Chair: Derek Hennen

1:15 p.m.         S2 Talk 1 Max Ragozzino

1:30 p.m.         S2 Talk 2 Tony Timpano

1:45 p.m.         S2 Talk 3 Heather Govenor

2:00 p.m.         S2 Talk 4 Mary Lofton

2:15 p.m.         S2 Talk 5 Zach Martin

2:30 p.m.         Poster Reception (students by posters)

3:30 p.m.         Platform Award Announcements

3:45 p.m.         Symposium Adjourns

 

All IGC fellows are encouraged to present their work at the symposium. Fellows have the option of presenting either a poster or a talk. Please indicate your preference by Friday, March 3rd. Awards will be given for best talks.

Abstracts for talks and posters should be submitted to Gloria Schoenholtz (schoeng@vt.edu) by March 31, 2017.  Each abstract should contain:

  1. Title
  2. Authors and Affiliations (e.g., Department and University)
  3. An abstract not to exceed 250 words in length

For posters: maximum poster size is 40″ x 60″.  An easel and backboard will be provided.

Surviving or thriving with malaria: the role of stress hormones in mediating resistance and tolerance

Authors: Laura A. Schoenle 1Ignacio T. Moore 1, Fran Bonier 1,2

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Biology Department, Queen’s University, Ontario, Canada

Glucocorticoid hormones provide a mechanism for individuals to rapidly adjust their physiology and behavior to meet the challenges of a variable environment. An individual’s baseline concentration of glucocorticoids can reflect life history stage and resource demands and affect a suite of physiological and behavioral responses that include immune modulation and resource allocation. Thus, glucocorticoids could facilitate a response to parasites that is optimized for an individual’s specific challenges and life history stage. We used an observational field study and a controlled experiment to test the role of glucocorticoids in mediating the response to Haemosporidian parasites (including those that cause avian malaria) in red-winged blackbirds (Agelaius phoeniceus). Among free-ranging birds, individuals with higher baseline concentrations of glucocorticoids experienced reduced costs of infection. However, we found no relationship between hormone levels and parasite burden. We then experimentally increased glucocorticoid concentrations in adult birds held in outdoor aviaries. In the aviaries, high-dose glucocorticoid treatment increased both birds’ parasite load and the cost of infection. Interestingly, the effects of treatment depended on co-infection status. Glucocorticoids might influence the response to infection by activating tissue repair or altering the strength of the inflammatory immune response. Our results suggest a potentially adaptive role for glucocorticoids in mediating the response to infection that could vary depending on the extent of the change in circulating glucocorticoid concentrations.

 

Life histories and invasions: accelerated laying rate and incubation time in an invasive lizard, Anolis sagrei

AuthorsTamara L. Fetters1 and Joel W. McGlothlin1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

During biological invasions, non-native invaders often experience environments that differ substantially from those found in their native range; these novel conditions can impose strong directional selection and lead to rapid phenotypic divergence between native and invasive populations. The brown anole (Anolis sagrei) is a small lizard native to Cuba and the Bahamas that has invaded the southeastern United States over the past century. Native and invasive populations experience different climatic variables with more northern invasive populations experiencing lower mean annual temperatures and shorter breeding season lengths than more southern native populations. Because invasion success hinges on the ability of a population to survive and expand, we hypothesized that invasive populations whose reproduction is limited by a shorter breeding season would experience strong selective pressure to decrease egg incubation time and the spacing between egg lays. We collected brown anoles from a native island population in the Bahamas and from 3 populations in the southeastern United States ranging from southern Florida to Georgia. We found that eggs from invasive populations hatched significantly faster than those from native populations, and that females from invasive populations had shorter intervals between egg lays than did females from native populations. Our results indicate that life-history traits have rapidly diverged during the brown anole invasion, potentially facilitating the species’ successful establishment and expansion.

 

How are we doing? Estimating lemur abundance in northern Madagascar

Authors: Brandon Semel 1, Sarah Karpanty 1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Primate populations face a myriad of threats related to climate and land use change, making long-term population monitoring critical to prioritizing conservation efforts. Ground-based line transects are typically conducted to estimate and monitor primate populations, unfortunately, this method may be inaccurate, costly, and logistically challenging. We sought to test whether unmanned aerial vehicles (UAV) could effectively monitor primate populations in a poorly studied region of northern Madagascar compared to traditional walking surveys.

Critically endangered golden-crowned sifakas and endangered crowned lemurs were found in all five of the surveyed forest fragments during walking surveys. Preliminary estimates suggest a 36% sifaka population decline from ~18,000 individuals in 2006/2008 to a current estimate of ~11,500 individuals (95% CI: 7,128-18,682). Crowned lemur densities are low (~15 individuals/km2) compared to other sites (29.81 individuals/km2) and abundance in the region is ~7,000 individuals (95% CI: 3,287-13,539). Evidence of lemur poaching was detected along several transects and active poaching was encountered in one forest fragments.

Sifakas generally did not exhibit a negative behavioral response to the UAV. However, it was difficult to detect lemurs from drone-captured imagery due to persistent leaf cover and a reduced overhead profile. Additionally, technical issues with the drone limited our ability to perform a complete cost-benefit analysis between walking and aerial transects and to collect new imagery for monitoring land cover change. Based on these field trials, we identified several improvements for future UAV primate surveys (e.g., FLIR camera, autopilot software) and for continued global change research in the region.

 

How to deal with a mixed up group: unraveling the species of the millipede genus Pseudopolydesmus (Polydesmida: Polydesmidae)

Authors: Derek A. Hennen 1 and Paul. E. Marek 1

Affiliation: 1. Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Millipedes are a large, diverse class of terrestrial arthropods found on all continents except for Antarctica. In North America, about 1,000 species are known from habitats ranging from deserts to forests. Despite their ubiquity in terrestrial habitats, the group remains poorly known, even among the common genera. The genus Pseudopolydesmus is ubiquitous in eastern North America, but its 12 species are poorly diagnosed and the genus is in need of revision using both morphological and molecular methods. Field work over the past year has resulted in fresh collections of Pseudopolydesmus specimens from across the eastern United States, focused particularly in the Appalachian Mountains. This field work, combined with the inspection of Pseudopolydesmus holdings from the Virginia Museum of Natural History and the North Carolina Museum of Natural Sciences, turned up three new species hypotheses and more detailed geographic distributions for Pseudopolydesmus species. Newly collected specimens form the basis for the first molecular investigation of intraspecific relationships within the genus, with preliminary results showing the species falling into two groups.

An update on EAB Biocontrol in Virginia

Authors: Max RagozzinoDr. Scott Salom1  Dr. Jian Duan2

Affiliations: 1. Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia  2.  USDA ARS

Since fall 2015, a total of 6 field sites in VA and NC were found where the EAB infestation is recently discovered, infested trees are suffering from less than 50% canopy dieback, and the trees are accessible and abundant. Sites include two private landowners in Blacksburg, VA & Natural Bridge Station, VA; two State Parks, Leesylvania State Park in Woodbridge, VA & Douthat State Park in Millboro, VA; one County Park, Mid-County Park in Christiansburg, VA; and Cherry Research Farm in Goldsboro, NC. EAB infestations varied from newly discovered to established for multiple years. In spring of 2016, 10,000 Tetrastichus planipennisi and 200 Spathius agrili were requested from USDA APHIS, Dr. Jian Duan provided 500 S. galinae. Each site was to receive 2000 adult female T. planipennisi, with a minimum of 500 adults per release. Due to field site characteristics, New River Junction in Blacksburg, VA received 1000 adults and Douthat State Park in Millboro, VA received 3000 adults. All other sites received approximately 2000 T. planipennisi. Yellow pan trap & larval sentinel log monitoring was set up at each site. So far T. planipennisi has been recovered only at Leesylvania State Park. Interspecies competition experiments were set up between S. agrili & S. galinae to determine the impact of competition. Due to high EAB larval mortality, the majority of trials were lost. Moving forward we have adjusted our sanitary procedures to prevent this from happening in the future. Emergence synchrony experiments are planned for S. agrilS. galinae.

 

Effects of coal mining on freshwater salinization and aquatic insect diversity

Authors: Tony Timpano1, Stephen Schoenholtz1, David Soucek2, and Carl Zipper3

Affiliations: 1. Department of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University; 2. Illinois Natural History Survey, U. Illinois Urbana-Champaign; 3. Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Human activities like agriculture resource extraction can increase the dissolved inorganic ion concentration (i.e., salinity) in waterbodies, creating toxic conditions for life adapted to dilute freshwater. This salinization of freshwaters is a global threat to aquatic biodiversity. In the USA, mountaintop coal mining contributes to salinization of headwater streams in the Appalachian region, a biodiversity hotspot. Salinization has been linked to widespread declines in diversity of aquatic insects, an important group that comprises much of the biomass in headwater streams and performs critical ecosystem functions. To mitigate such biotic impacts, a thorough understanding is needed of the nature of stream salinization as well as how the insect community responds to increased salinity. Toward that end, we measured the salinity surrogate electrical conductivity continuously for four years in 25 minimally-disturbed headwater streams across a gradient of salinity in the Appalachian coalfields of Virginia and West Virginia. In addition, we surveyed the aquatic insect community multiple times over the same period. We found that salinity followed a predictable annual cycle, exhibiting a minimum in spring and maximum in autumn, deviating up to ± 20% from annual mean salinity. We also observed seasonal differences in overall insect community composition, as well as declines in insect diversity and abundance in streams with increased salinity. Finally, we identified salt concentrations likely to cause diversity reductions. Our salinity models, combined with information about insect community responses to salt, can aid management of salinization to achieve aquatic biodiversity goals.

 

Relative importance of suspended, dissolved, and bedded sediment form on macroinvertebrate community health in Virginia streams

Authors: Heather Govenor1, Lawrence Willis2, Leigh-Anne Krometis1, and W. Cully Hession1

Affiliations: 1. Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 2. Virginia Department of Environmental Quality, Roanoke, Virginia

Human manipulation of the landscape through agriculture, urbanization, and resource extraction has led to substantial increases in sediment loadings to freshwater streams and rivers. Excess sediment is a primary cause of aquatic life impairments nation-wide. Current management practices involve reducing landscape loadings in impaired watersheds to levels consistent with those of paired reference watersheds. This approach does not consider the multiple physical forms sediment takes upon reaching the stream channel (e.g., dissolved, suspended, and bedded states), or the variety of impacts different sediment forms have on aquatic life. Determining the relative importance of the physical forms of sediment on biological response is a necessary first step toward identifying useful management endpoints and improving predictions of the potential effectiveness of restoration efforts. We assessed ten years of Virginia Department of Environmental Quality habitat and macroinvertebrate community monitoring data spanning five bioregions to evaluate the relative influence of 9 sediment metrics on stream health as measured by the Virginia Stream Condition Index (VSCI), a macroinvertebrate community biometric. Metrics reflecting the stream bed had more influence on the VSCI than did suspended or dissolved sediment metrics. Mean reach embeddedness had the most influence on overall stream condition (VSCI) and other commonly used pollution-sensitive metrics. We are currently developing a sensitivity threshold for embeddedness based on extirpation rates of invertebrate families. Thresholds of response may play a key role in water quality management actions including stressor identification, setting of restoration goals (e.g., total maximum daily load development), and monitoring of restoration effectiveness.

 

 
Storms can both stimulate and inhibit phytoplankton communities: lessons from a whole-ecosystem lake mixing experiment

Authors: Mary E. Lofton 1, Ryan P. McClur1, Shengyang Chen2, Charlotte W. Harrel 1, Jonathan P. Doubek 1, Nicole K. Ward 1, Madeline E. Schreiber 3, John C. Little 4, Cayelan C. Carey 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. University of Sydney, School of Civil Engineering, Sydney, Australia; 3. Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 4. Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

In lakes and reservoirs worldwide, increased nutrient concentrations have led to an increase in harmful phytoplankton blooms. Blooms can cause hypoxia in the bottom waters of lakes and reservoirs, alter freshwater food webs, and impair drinking water quality. Some evidence suggests that phytoplankton may increase under future climate conditions, but this is largely based on predictions of warmer temperatures, which favor bloom-forming cyanobacteria. The responses of phytoplankton to other climate factors are less clear. Specifically, many regions are expected to experience future increases in storm intensity, which may alter phytoplankton community structure and bloom frequency through increased water column turbulence. To improve understanding of phytoplankton community responses to storms, we used an engineered epilimnetic mixing system to conduct two whole-ecosystem storm simulation experiments in a small drinking water reservoir in summer 2016. We monitored phytoplankton community dynamics throughout the water column with high-frequency fluorescence profiles and compared these data to phytoplankton concentrations in a non-manipulated reference reservoir. Our results suggest that the intensity and duration of storm events can alter phytoplankton community response to mixing. Specifically, we observed that short (<6 hours), intense mixing events stimulated phytoplankton, including cyanobacteria, potentially by entraining nutrients from below the thermocline into the surface waters. In contrast, less intense mixing events of longer duration (>20 hours) had a negative effect on green algae, but did not affect other taxa. Our work indicates that storms may stimulate and inhibit phytoplankton, and underlines the importance of considering whole-ecosystem dynamics when predicting global change effects on phytoplankton.

 

Multi-level impacts of coal mining on stream fishes in the Clinch River and Powell River watersheds of Virginia

AuthorsZachary Martin1, Serena Ciparis1, Paul Angermeier1,2, and Don Orth1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. U.S. Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Mining coal has altered water quality and stream habitats in Appalachian headwater streams beyond tolerances of aquatic communities; however, regulators struggle to agree on water quality standards for coalfields streams proposed by the U.S. Environmental Protection Agency based on macroinvertebrate sensitivities. Our multidisciplinary research evaluates fish responses at community-, population-, and individual-levels to mining stressors to advance conversations about such standards. Water quality, physical habitat, and fish samples were collected at 83 2nd– to 4th-order streams representing a mining-intensity gradient in the Clinch River and Powell River watersheds based on mining extents within watersheds; conductivity and several major ion concentrations from our surveys were positively related to the gradient. We expected occurrence (e.g. species and trait) and physiology (e.g. enzyme activity) responses along these gradients, especially conductivity. We modeled occurrence with boosted regression trees, using mining intensity, watershed characteristics, instream habitat, geomorphology, water quality, and spatial structure among sites as predictors. Etheostoma flabellare and insectivore occurrence responded negatively at approximately 330 µS/cm, aligning with proposed regulations. Campostoma anomalum occurrence also responded to conductivity, albeit in positively. We also identified suppression of glutathione reductase activity in E. flabellare associated with high mining intensity likely related to energetic limitations. Rhinichthys obtusus occurrence was not affected by mining intensity but activity of the selenium-dependent enzyme glutathione peroxidase was positively related to mining intensity. Our results may reflect the indirect stress of food resource (i.e., macroinvertebrates) limitation in mining-impacted streams playing a role in trait-specific fish extirpations, confirming the relevance of a macroinvertebrate based standard.

The influence of social behavior and stability on disease transmission in a songbird host

Authors: Matt Aberle 1, James Adelman 2, Sahnzi Moyers 1, Dana Hawley 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Natural Resources and Ecology Management, Iowa State University, Ames, Iowa.

Human wildlife provisioning has long been overlooked as a major ecological factor, but in the last ten years it has been shown to be an important factor on the social behavior and physiology of wildlife and, consequently, disease. A prime example is among house finches (Haemorhous mexicanus) who, since the mid-1990s, have been subject to infection with a highly contagious bacterium, Mycoplasma gallisepticum, which causes debilitating conjunctival pathology. House finches congregate at bird feeders in social flocks, where most transmission takes place, making it an ideal system for testing hypotheses regarding how human provisioning influences social behavior, physiology, and disease transmission. To test the impact of bird feeders, I altered feeder density across several sites on the Virginia Tech campus while using radio-frequency identification to track social networks and individual behavior. By altering the density of feeders, my results should be able to show the effects of human feeding via bird feeders on this disease system by seeing changes in the social networks of house finches, individual behavior and physiology, and the prevalence of disease.

 

 
Loblolly pine and switchgrass: A year of eddy flux measurements in Virginia

Authors: Benjamin J. Ahlswede 1, R. Quinn Thomas 1, Tom O’Halloran 2

Affiliations: 1. Department of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University; 2. Forestry and Environmental Conservation Department, Clemson University

How do land-use transitions affect climate? Land-use is a large component of human emissions of CO2 to the atmosphere. But these transitions have immediate, local, biophysical impacts on surface climate as well. As climate change continues the market for biophysical effects and other climate services will continue to grow. What land-types provide the greatest climate services in the southeastern United States?

We have been gathering data from the eddy flux covariance systems at Sweet Briar College in central Virginia for the past year. These two towers measure fluxes of water, carbon and energy as well as relevant meteorological measurements over a switchgrass field and a loblolly pine stand respectively. These measurements allow us to make assessments of the exchange of carbon and the biophysical effects on climate.

After a year of data, the switchgrass field shows the most biophysical benefit. This is mostly due to its high albedo. In addition, the switchgrass has a higher rate of carbon absorption than loblolly pine during peak growth. However, this must be contrasted with the large amount of CO2 emitted by the grass system during non-peak growth, ultimately making it a net source of carbon. The Pine system continues to be a carbon sink all year, but what fluxes may emerge after a harvest event remains unknown.

 

Identifying local strains of Nile tilapia Oreochromis niloticus that are adapted to future climate conditions

Authors: Gifty Anane-Taabeah 1,2Emmanuel Frimpong 1, Stephen Amisah 2, Akwasi Ampofo-Yeboah 3, and Eric Hallerman 1

Affiliations: 1. Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Fisheries and Watershed Management, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, 3. Department of Fisheries and Aquatic Resources Management, University of Development Studies, Nyankpala Campus, Ghana

This study was conducted to synthesize information on the ambient water quality (temperature, dissolve oxygen and salinity) for the Nile tilapia, an important commercial species, compare wild populations in the Volta basin and the selectively bred Akosombo strain from the basin used in fish farming in Ghana under current and future climate conditions, and develop predictive models delineating the boundaries of the species’ range. A combination of literature survey, field and laboratory methods provided data for meta-analysis, growth and genetic analysis, as well as distribution models. We found variations in water temperature along the latitudinal gradient in Ghana; and temperature was the most informative variable in terms of characterizing the adaptive range and ambient water quality for the species. The results of the growth studies showed no evidence of superior performance of the Akosombo strain over the wild strains under current or predicted future climatic conditions of temperature, dissolved oxygen, or salinity. Significant Fst values from the genetic analysis suggested that the Akosombo strain was well differentiated from all the wild populations (Aframso, Sabare and Binaba) studied. The combined results of the field, growth and genetic studies show that at least one wild population from the Oti River (Sabare) may possess the traits for superior performance under high temperature and low DO conditions. Further studies should concentrate on comparing the Sabare strain with the Akosombo strain under different experimental conditions and increase replications to confirm the suggested differences and the heritability of those performance traits for selective breeding.

 

Tree-of-Heaven (Ailanthus altissima) biocontrol

Authors: Rachel Brooks 1, Scott Salom 2, Anton Baudoin 1

Affiliations: 1. Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Abstract: Ailanthus altissima, commonly known as the tree-of-heaven, has been successfully invading the North American landscape since its introduction from China over 200 years ago. Today, it is found in over 40 states along transportation corridors, on agricultural fields, within urban areas, and in forest stands displacing native species. Long-term and wide-spread control using chemical and mechanical methods have been ineffective in containing this tree. Recently, two strains of naturally occurring fungi (Verticillium nonalfalfae and V. dahliae) have caused entire Ailanthus stands in Ohio, Pennsylvania, and Virginia to decline and die, effectively removing the invasive species from the area. Preliminary work from Pennsylvania shows that V. nonalfalfae has the potential to become a cheap, effective, and safe biocontrol agent. This summer, we will determine if these two fungal pathogens also have the potential to become effective control agents in Virginia. Ailanthus stands throughout Virginia have been identified and mapped, and conidia suspensions of one or both species will be injected into the trees in May. Disease progression and spread will be monitored monthly and analyzed to compare differences between hardiness zones. Has our environment given us an effective tool to fight this aggressive invader?

 

Hypoxia-induced trade-offs on zooplankton vertical distribution and community structure in reservoirs

AuthorsJonathan P. Doubek 1, Kylie L. Campbell 1, Kaitlyn M. Doubek 1, Kathleen D. Hamre 1, Charlotte W. Harrell 1, Mary E. Lofton 1, Ryan P. McClure 1, Nicole K. Ward 1, and Cayelan C. Carey 1

Affiliations: 1. Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia

Because of global change, lakes and reservoirs worldwide are increasingly experiencing low dissolved oxygen concentrations (hypoxia). Although the effects of hypoxia on internal nutrient loading have been well-studied, less is known about how hypoxia impacts plankton communities, especially zooplankton. Typically, zooplankton migrate to the dark bottom waters (hypolimnion) during the day to escape visual fish predation in the well-lit surface waters (epilimnion). However, due to the physiologically-stressful conditions of hypoxic hypolimnia, zooplankton may remain in the epilimnion during daylight, trading oxic stress for increased predation risk. We sampled five reservoirs weekly to biweekly during the daytime in southwestern Virginia, USA over three summers to examine how hypolimnetic oxygen concentrations impact the vertical distribution, density, biomass, and community composition of macrozooplankton and rotifers. These reservoirs varied on a gradient of hypolimnetic oxygen concentrations, from no oxygen to high oxygen during the sampling period. In addition, we also conducted ten 24-h sampling campaigns on reservoirs across this same oxygen gradient to examine how zooplankton were vertically distributed over day-night periods. Under hypoxic conditions, zooplankton were predominately found in the epilimnion during the day and night, did not exhibit diel vertical migration, and had overall lower densities and biomass than in reservoirs that exhibited oxic hypolimnia. Only two zooplankton taxa were found predominately in hypoxic zones. Zooplankton play a critical role in lakes and reservoirs as the dominant grazers of phytoplankton, and our results suggest that hypolimnetic hypoxia may alter zooplankton vertical distribution and densities, which may in turn exacerbate water quality degradation.

 

Mathematical modeling of cyanobacterial dynamics in a chemostat 

Authors: Fadoua El Moustaid 1, Ross P. Carlson 2, Federica Villa 3, Isaac Klapper 4

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Center for Biofilm Engineering, Montana State University, Bozeman, MT; 3. Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Milano, Italy; 4. Department of Mathematics, Temple University, Philadelphia

We present a mathematical model that describes how cyanobacterial communities use natural light as a source of energy and water as a source of electrons to perform photosynthesis and therefore, grow and co-survive together with other bacterial species. The purpose of our model is to explain interactions between bacteria. In particular, we apply our model to a phototrophic population of bacteria, namely, cyanobacteria. Our model involves the use of light as a source of energy and inorganic carbon as a source of nutrients. First, we study a single species model involving only cyanobacteria, then we include heterotrophs in the two species model. A stability analysis is done and the obtained results show that adding heterotrophs increase the level of inorganic carbon in the medium which allows cyanobacteria, on one hand, to perform more photosynthesis, therefore increase their growth and on the other hand delay the excess of light damage which also benefits cyanobacterial growth.

 

Temporal variation of the skin microbiome in lowland amphibians and its implications for conservation

Authors: Angie Estrada 1, Myra C. Hughey, Eria A. Rebollar, Matthew H. Becker, Jenifer B. Walke, Daniel Medina 1, Roberto Ibáñez, Reid N. Harris and Lisa K. Belden 1

Affiliations1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

The amphibian skin microbiome has been the focus of recent studies aiming to better understand its role in host defense against disease. However, host-associated microbial communities can be dynamic, and changes in their composition can influence their function. Understanding temporal variation of bacterial communities on amphibian skin is critical for establishing baselines from which to improve the development of mitigation techniques based on probiotic therapy and provide long-term host protection in a changing environment. Here, we investigated whether microbial communities on amphibian skin change over time across seasons and years at a single pond. To examine this, we collected skin swabs from two pond-breeding species of treefrogs (Agalychnis callidryas and Dendropsophus ebraccatus) for four years in a single lowland tropical pond in Panama. Relative abundance of OTUs based on 16S rRNA gene amplicon sequencing was used to quantify bacterial community diversity on the skin. We found variation between the two species within the same pond. In addition, we found significant variation in bacterial community structure across years for both speciesWe also found significant changes across seasons, but this was stronger in D. ebraccatus. Lowland amphibians species persist despite the presence of a fungal skin pathogen, Batrachochytrium dendrobatidis, which has caused declines in highland populations. These preliminary findings suggest that skin-associated microbiomes vary across time, but more research is necessary to elucidate the significance of temporal variation in bacterial skin communities and their maintenance for amphibian conservation efforts.

 

The role of biotic and abiotic factors in the distribution limits of an invasive grass

Authors: Rebecca Fletcher1, Daniel Atwater1, David Haak1, and Jacob Barney1

Affiliations: 1. Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Since before the time of Darwin, there has been an interest in species distributions and why species are found where they are. Range limits are strongly associated with both abiotic factors (e.g., temperature, precipitation) and biotic factors (e.g., competition, predation), but it is still unclear how much each of these factors influence species’ ranges. Recently, in light of global change, there has been a resurgence of interest in species distributions as the need to accurately predict how species will respond to climate change becomes ever more important. This need is especially important when considering invasive species, as evidence indicates that some invasive species may be expanding their ranges in response to climate change. The invasive Johnsongrass (Sorghum halepense) is a highly damaging weed and invader of natural ecosystems that has a wide, global distribution; however, there is evidence that climate may play an important role in limiting its range. We are investigating the influence of climate and competition on the range limits of Johnsongrass through the use of reciprocal common gardens in 5 locations–New York, Virginia, Georgia, Texas, and New Mexico–that represent the peripheral, edge, and core of Johnsongrass’ US distribution along both a temperature (NYàVAàGA) and precipitation (GAàTXàNM) gradient. Each common garden will have a no competition and a competition treatment. This design enables us to investigate the potential biotic and climate drivers of Johnsongrass’ distribution limits. Our work will advance our understanding of the factors that influence the distribution and abundance of invasive species.

 

Global change impacts on microbiome mediated plant-pollinator interactions.

Authors: Ariel Heminger 1 and David Haak 1

Affiliations: 1. Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Pollinators form the cornerstone of ecosystem stability and agricultural production and they are under threat from multiple global change factors which lead to precipitous declines in pollinator health. Recent declines in bee health have been associated with changes in gut microbial communities. Additionally, bee gut microbiomes leave a ‘footprint’ on flower microbiomes, however, little is known about the reciprocal effects of the floral microbiome on bee gut microbial communities, nor the impacts of global change factors in shaping these interactions. Here we compare reciprocal microbiome responses in pollinators and flowers across a latitudinal gradient (a surrogate for elevated temperature) and between native and non-native Solanum species. First, we will assess the structure of the floral microbiome during floral development and assess how they correspond with changes in pollinator gut microbial communities. Next, flowers on both species will be caged to exclude pollinators to determine how pollinators are impacting the floral microbiome in each species. The analysis of microbial communities in both plant species and their pollinators will be conducted through sequencing the 16s rRNA gene and ITS region as appropriate. Plant fitness will be assessed and determined how it relates to floral microbiome. This study will provide information regarding differences between native and non-native species microbial communities, how changes in floral microbiome structure impact pollinators, and how changes in environmental factors shape plant-pollinator microbiome interactions.

 

Sexually transmitted microbes as a cost of extra-pair activity in female tree swallows

Authors: Jessica Hernandez 1 and Ignacio Moore 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Up until the 1980s, most avian species were considered to be truly monogamous. It was not until the recent advent of revolutionary genetic approaches that the opposite pattern was shown to be true of avian mating systems. Species that were previously recognized to be truly monogamous were found to have extra-pair young, thus exhibiting evidence for extra-pair copulations. Fundamental questions in biology center around understanding the advantages and disadvantages of monogamy versus polygamy, particularly with regards to females and polyandry. While females face numerous potential fitness trade-offs (e.g., benefits: good genes, genetic diversity in offspring; costs: loss of paternal care, de novo deleterious mutations), I will focus on the sexual transmission of pathogenic microbes, which has been suggested to be a cost of extra-pair copulations to females since as early as the 1970s, but has not yet been adequately tested. For my dissertation, I will study a free-living, box-nesting population of polyandrous female tree swallows (Tachycineta bicolor) that form a social pair bond with a male throughout the breeding season, yet also engage in extra-pair copulations. Through observational and experimental studies, this project will help elucidate the relationship between extra-pair copulations and the presence, prevalence, and pathogenicity of sexually transmitted cloacal microbiota, with respect to fitness, in a wild avian population. Overall, such research is essential since host fitness consequences of sexually transmitted microbes likely influence sexual selection and the evolution of mating systems.

 

Implications of a changing climate on bird development

Authors: Sydney F. Hope 1, Sarah E. DuRant , Robert A. Kennamer 3William A. Hopkins 1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, VA; 2. Department of Integrative Biology, Oklahoma State University; 3. Savannah River Ecology Lab, University of Georgia

Our changing climate may pose a threat to the early developmental environment of animals. The effect of climate change on developing reptiles is well-studied, and there is evidence that changes in incubation temperature can have substantial effects on offspring. In contrast, the effects of temperature changes on bird phenotypes have been historically overlooked because parents regulate incubation temperature. However, studies have shown that changes in the environment can affect avian parental incubation behavior, and that small changes in incubation temperature can affect avian offspring phenotypes. Yet, few studies have investigated how environmental changes may directly and indirectly influence incubation temperature, and no studies have investigated how incubation temperature influences avian offspring behavior. We used wood ducks as a model system to address these questions. Our results show that wood duck nests with the largest clutch sizes and the lowest ambient temperatures led to the lowest incubation temperatures. We also found that ducklings incubated at 35 and 37°C exhibited bolder and more exploratory behaviors than those incubated at 35.8°C, while those incubated at 35°C were less successful at exiting the nest (a crucial behavior for wood duck ducklings) than those incubated at the other two temperatures. This research shows that environmental changes influence avian incubation temperature and thus, may influence offspring behaviors that are critical for survival. In this case, warming temperatures may be beneficial to developing birds, but future work should address how extreme weather events or changes in food availability due to climate change affect incubation temperature.

 

A Division of the Crown: using novel tracking devices to examine behavioral responses to fragmentation and habitat heterogeneity in crowned lemurs (Eulemur coronatus)

Authors: Meredith Keeley1, Ignacio Moore1, and Nicole Abaid2

Affiliations: 1Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Madagascar, an island off the coast of southeast Africa, is one of the world’s “richest” biodiversity hotspots, yet little is known about how habitat degradation will affect imperiled species. Crowned lemurs (Eulemur coronatus), listed as endangered on the IUCN red list, are frugivorous, group living, cathemeral primates endemic to forests of northern Madagascar. Crowned lemurs display a flexible behavioral strategy called fission-fusion, which results in individuals periodically separating from group members (fissions) and rejoining after temporal and spatial separation (fusions). We are seeking to examine how fragmentation and landscape heterogeneity influence fission-fusion dynamics in this species. However, studying primates when groups are constantly fluctuating in size and composition is nearly impossible due to logistical challenges and the high cost of commercially available tracking equipment. To address this issue, we propose to design a modular, open-source tracking collar. Our monitoring device, nicknamed FitPET (“FITness, Proximity, Energetics, and Tracking”), will be capable of capturing data on lemur social and spatial behavior. The tracking devices will be specialized to collect precise measurements of proximity between group members, grooming frequency, locomotion, and heart rate. The outcome of the project will be the development of technology, synergizing the fields of biology and engineering, to better understand crowned lemur social interactions and transform the ways in which wildlife species are studied.

 

Urbanization and parental care: Are parents able to compensate for changing ecological conditions?

Authors: Samuel Lane 1, Kendra Sewall 1

Affiliation: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Phenotypic plasticity is an organism’s ability to adjust its phenotype in response to habitat variation. Such plasticity has been proposed to help organisms cope with changing environmental conditions. Additionally, parental care is a mechanism that could buffer developing young from environmental variation with consequences for their mature phenotype. For my dissertation, I will compare phenotypic outcomes of free-living, urban and rural song sparrows to better understand how variation in habitat quality affects growth and development.  I will use observational and experimental approaches to study the following objectives: 1) To determine the level of developmental stress offspring experience, I will measure nestling growth and stress hormone levels through development. I predict that offspring’s in urban habitats will experience pathological stress during development. I predict that urban habitats will be of lower quality due to food restriction and anthropogenic stressors. 2) To determine the extent to which parental care may mitigate ecological variation, I will use video recordings of the nest to measure feeding rates and food load. I predict that parents in urban environments will increase parental care when possible but prioritize territorial behaviors. Collectively, these studies will resolve how urbanization affects the phenotype and fitness of developing birds. Urbanization represents a dramatic and relatively quick change in environment. Understanding how environmental factors impact birds’ phenotypes, if parental care provides a buffer to ecological change, and the fitness consequences of urbanization will inform conservation efforts.

 

Advancing equity: Comparing water violations in rural versus urban Virginia

Authors: Cristina E. Marcillo 1Leigh-Anne Krometis 1

Affiliations: 1. Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

The Safe Drinking Water Act (SDWA) of 1974 and its subsequent amendments have revolutionized the way that drinking water is protected in the United States. However, high profile failures, such as the lead crisis in Flint, Michigan, have cast doubt on the equity and reliability of these regulatory mechanisms. Previous studies using publically available compliance data have found that regulatory inequities regarding water quality and availability do exist based on system size, race, ethnicity, and low socioeconomic status of the community served. However, the effects of urbanity and rurality on drinking water system integrity has only been cursorily characterized. This work seeks to identify and describe primary differences in drinking water challenges in urban and rural American landscapes. The work to be presented is an illustrative case study comparing drinking water violation patterns in distressed rural Appalachia counties versus coastal Virginia cities designated as environmental justice hotspots. Initial comparisons suggest that rural Virginia counties are served by five to twelve times the number of water systems as the two independent cities, despite serving less than twenty-five percent of these cities’ population. More notably, over one hundred times the number of SDWA violations were reported within the rural region as compared to the independent cities within the last ten years. Ongoing work is expected to expand this case study method to the entire southeast region of the United States. This study has implications for the way that public water systems are managed and regulated across disparate regions of the United States. This work also has value for rapidly urbanizing developing nations who must manage their drinking water infrastructure for a growing urban and peri-urban population.

 

Metalimnetic oxygen minimum zones decouple diffusive CH4 and CO2 fluxes from seasonal turnover in a eutrophic reservoir

Authors: R.P. McClure1, M.E. Lofton1, K.D. Hamre1, B.R. Niederlehner1, Z.W. Munger2, S. Chen3, J.P. Doubek1, M.E. Schreiber2, and C.C. Carey1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 3. Department of Civil Engineering, University of Sydney, Sydney, Australia

Diffusion of greenhouse gases (GHGs) from freshwater ecosystems into the atmosphere can contribute a large fraction of total GHG efflux. In temperate waterbodies, annual peak diffusive flux generally occurs during fall turnover when methane (CH4) and carbon dioxide (CO2) in the anoxic bottom layer (the hypolimnion) mix to the surface. However, when thermal stratification develops, some waterbodies become anoxic in the middle of the water (the metalimnion), not the hypolimnion. This can change the distribution of pCH4 and pCO2 in the water column and alter diffusive CH4 and CO2 efflux phenology. As a part of water quality management in a local reservoir, an anoxic metalimnion (OMZ) has developed since 2013. We measured depth profiles of dissolved CH4 and carbon dioxide (CO2) concentrations since 2015, and estimated CH4 and CO2 atmospheric gas exchange with multiple gas flux models. We observed substantial accumulation of CH4 within the OMZ of the local reservoir in summers 2015 and 2016. Regardless the gas flux model, the largest efflux of CH4 into the atmosphere was decoupled from turnover both years, while peak CO2 efflux from the hypolimnion occurred during turnover. Thus, timing and magnitude of GHG fluxes may be dependent on the depth of the gases in the water column, and that the efflux of gases in the metalimnion may be sensitive to extreme events that are decoupled from turnover. If OMZs increase as a result of global change, waterbodies may accumulate substantial concentrations of CH4 in their water columns, thereby altering the GHG efflux phenology.

 

Resource use and interspecific interactions in a cavity-nesting guild in central Namibia

Authors: David Millican 1, Mark Stanback 2Jeffrey Walters 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Biology, Davidson College, North Carolina

Cavity-nesting guilds are hierarchical communities of vertebrates and invertebrates that interact through competition for nest sites. Some species in these communities, known as primary excavators, are able to create their own nest cavities. Other species, known as secondary nesters, rely on pre-existing cavities to breed, be they cavities made by excavating species or by other natural processes. Due to their dependence on pre-existing cavities, secondary nesters are highly susceptible to forms of disturbance that diminish the availability of suitable nest cavities, including anthropogenic management and natural disasters. Quantifying the entirety of a cavity guild’s structure is critical to understanding how to conserve that community. To inform land managers on how to preserve Namibia’s threatened cavity-nesting guild, we have embarked on a nest-web analysis outside Otjiwarongo in central Namibia. We are two years into a study that aims to evaluate the availability of the central resource (tree cavities), primary forms of cavity creation, species-specific cavity preferences, and interactions between cavity-nesters, including direct competition for nest sites and indirect interactions as cavities are used over time. Preliminary results suggest that cavity density overall is low, with natural cavities (12.4/ hectare) 15 times more abundant than excavated cavities (0.8/hectare), and that large cavities are in particularly low supply. Some small-bodied secondary nesters readily use excavated cavities, suggesting that excavating species, though in low densities, may act as ecosystem engineers in this ecosystem. Large-bodied secondary nesters, of which there are over a half dozen species, are particularly likely to be restricted by cavity availability, as they utilize a limit supply of naturally formed cavities. Already facing intense competitive pressures, cavity-nesting populations could face declines due to pressures resulting from common management practices, such as charcoal production, as well as from climate change induced droughts, which may hinder floral growth, and thus the replacement of large, cavity-bearing trees. Results of this study will inform management plans and aid local conservation efforts targeting cavity-nesting species, some of which may risk extirpation from Namibian forests.

 

Natal dispersal patterns and behavior in juvenile male Red-cockaded Woodpeckers

Authors: Leah D. Novak1, Jeffrey R. Walters1, and Dylan C. Kesler2

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg; VA. 2. The Institute for Bird Populations, Point Reyes, California

Natal dispersal, the movement of an individual animal from its birth site to its breeding site, is primarily governed by resource quality and availability, and intraspecific competition for that resource. Natal dispersal can be costly, therefore juveniles often use a prospecting strategy to gain knowledge regarding the conditions outside their natal territory before permanently leaving. The Red-cockaded Woodpecker (RCW) is a cooperatively breeding, federally listed, endangered species endemic to open, southern pine savannah of the Atlantic and Gulf Coastal Plains. Juvenile male RCWs employ two natal dispersal strategies to cope with limited availability of resources, mainly cavities: the dominant males delay dispersal and remain on their natal territory as non-breeding helpers and the subordinate males disperse their first year. Juvenile female RCWs usually disperse, but prospect extensively before leaving. It is unknown if dominant and subordinate juvenile males also prospect. In this study, I investigated dispersal behavior, specifically prospecting behavior, in dominant and subordinate juvenile male RCWs in coastal NC. I followed 9 subordinate and 11 dominant juveniles before and during the breeding seasons (February – June) of 2015 and 2016 using radio telemetry and GPS while they prospected alone and while they foraged with their families. I then determined the distance and direction of forays and calculated the likelihood that a juvenile RCW would travel through certain cover types or near other conspecifics. Overall, subordinate males tended to prospect often and avoided other clusters, while dominant males tended to prospect less.

 

You can’t plant generic trees

Authors: Joshua M. Rady 1, Benjamin J. Ahlswede 1, R. Quinn Thomas 1

Affiliations: 1. Department of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University

It is well established that forests play a major role in global climate.  Trees take up ~30% of anthropogenic carbon dioxide, decreasing the warming impact of human emissions.  For this reason, forests play a role in many global warming mitigation approaches through reforestation and afforestation.  Current global climate models use simplified representations of forests that do not provide information critical to planning actual mitigation efforts.  Planting forests is not a binary decision.  You must also determine which species to plant, where, and what if any management to invoke.  We are currently working to improve a widely used global earth system model (NCAR’s CESM1.2 / CLM5) by incorporating more realistic representations of forest management and tree species.  With these improvements, we hope to answer several consequential questions:  Does forestry management impact the climate services provided by forests?  Which sequester more atmospheric carbon, natural or plantation forests?  What management activities might be employed to increase climate benefits?  What species should be planted and where to achieve certain climate goals?  Are the effects of some management actives, such as fertilization and irrigation, counteracted by downstream ecological effects?  The answers to these questions should be directly relevant to decision makers in the climate policy arena.

 

Individual variation in testosterone and cooperative behavior in a neotropical lekking bird, the Wire-Tailed Manakin

Authors: Ben Vernasco 1Ignacio Moore 1, Brent Horton 2, & T. Brandt Ryder 3

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 2. Millersville University, 3. Smithsonian Migratory Bird Center

­Manakins of the family Pipridae are known for performing complex courtship displays at leks. These complex displays have evolved in association with strong reproductive skew, suggesting individual differences in courtship behavior exist. By measuring components of hormone regulatory networks, one may be able to elucidate the proximate mediators of individual variation in courtship behavior. To date, however, work documenting the relationship between individual variation in reproductive behavior and circulating steroids in manakins has been inconclusive. Here, using video recordings of male territories and subsequently collecting a blood sample, we quantified the relationship between individual variation in reproductive behavior and circulating testosterone in male wire-tailed manakins (Pipra filicauda). In this system, previous research has shown that territory-holding males have higher testosterone than floaters (i.e., non-territory-holding males), implying that testosterone plays a role in territory acquisition and maintenance. Our results show that that males with a higher proportion of cooperative displays (an important predictor of male wire-tailed manakin reproductive success) perform longer displays. However, males with high circulating testosterone engage in fewer cooperative display bouts suggesting that high levels of testosterone may interfere with effective cooperative behavior and result in shorter display bouts. These results suggest that individual differences in circulating testosterone levels play an important role in mediating individual variation in male reproductive behavior and potentially success. This research ultimately adds to our knowledge about the proximate mechanisms that mediate individual variation in both reproductive and cooperative behavior.

 

Identifying early warning indicators of eutrophication to inform real-world management: engaging long-term data, ecosystem modeling, committed citizen scientists, and remote sensing

Authors: Nicole K. Ward 1, Bethel Steele 2, Kathleen C. Weathers 2, Kathryn L. Nottingham 3, Holly A. Ewing 4, Paul C. Hanson 5, Robert Wood 6, June Fichter 6, Cayelan C. Carey 1

Affiliations: 1. Virginia Tech, Department of Biological Sciences, Blacksburg, Virginia, 2. Cary Institute of Ecosystem Studies, Millbrook, New York, 3. Dartmouth College, Department of Biological Sciences, Hanover, New Hampshire, 4. Bates College, Program in Environmental Studies, Lewiston, Maine, 5. University of Wisconsin-Madison, Center for Limnology, Madison, Wisconsin, 6. Lake Sunapee Protective Association, Sunapee, New Hampshire

Freshwater lakes integrate the cumulative impact of upstream human activities on water quality, and thus early warning indicators (EWIs) of ecosystem change in lakes may be used to understand the impact of environmental changes in their catchment. EWIs are statistical metrics applied to high-temporal frequency data to predict regime shifts. To date, EWIs have been used to retroactively assess observed regime shifts and to reverse algal blooms in lakes, but they have not been widely used to inform real-world management decisions. Here, we explored the use of EWIs in water quality management by addressing the questions: 1) How are land use and climate change interacting to affect water quality in an oligotrophic lake over three decades? and 2) Can we use EWIs to manage water quality in a real-world oligotrophic lake? We used historical and recent GLEON (Global Lakes Ecological Observatory Network) buoy sensor data on Lake Sunapee, New Hampshire (USA), collected primarily by committed citizen scientists, to calibrate a lake ecosystem simulation model (General Lake Model; GLM) run at an hourly time step for three decades. We then tested for EWIs in the model output using a suite of statistical analyses, including breakpoint analysis, rolling standard deviation, and autocorrelation. The EWI assessment and simulated lake response to nutrient loading using GLM provide a suite of alternative scenarios as a tool to assist management. Our next steps are to assess land cover change using Landsat imagery and develop spatially-explicit nutrient loading model scenarios to predict future lake water quality

 

Ecological effects of livestock antibiotics on agricultural soils

Authors: Carl Wepking 1Brian Badgley 2Jeb Barrett 1, Matt Hedin 1, Katharine Knowlton 3, Kevan Minick 4, Partha Ray 5Mike Strickland 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 3. Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 4. Department of Forestry and Environmental Resources, North Carolina State University, North Carolina; 5. School of Agriculture Policy and Development, University of Reading, Berkshire, United Kingdom

Antibiotic use is under increased scrutiny due to their declining effectiveness; this includes the use of antibiotics in livestock production, which accounts for 80% of national antibiotic use. Much of this 80% passes through livestock via manure, with high estimates at approximately 14-million kg-yr-1. Studies have shown that additions of manure from cattle treated with antibiotics can have effects on soil microbial community composition, antibiotic resistance gene (ARG) abundance, and ecosystem functioning. However, studies have also shown that additions of manure from cows receiving no antibiotics can also cause increases in ARGs. To better understand the relative contribution of manure and antibiotics, a common garden experiment was established where plots were amended with manure from cattle either treated with one of two types of antibiotics, or untreated cattle. Manure was added monthly for three years. Each spring, plots were pulse-labeled using 13C and 15N. Soils and plant biomass from these plots were collected and analyzed using a range of assays to better understanding how soil microbial communities are impacted by manure as well as antibiotics. We have found that manure type does have an impact on a number of important microbial parameters. For instance, manure from cattle treated with the antibiotic pirlimycin elicited an ~6,000 kg ha-1 y-1 increase in respired carbon compared to manure from cattle treated with cephapirin. Although further analysis needs to be completed, the results from this field study highlight the potential influence antibiotics and the type of antibiotics have on soil and ecosystem processes.

 

Life history and ecology of the endangered Bahama Swallow (Tachycineta cyaneoviridis)

Authors: Maya Wilson 1 and Dr. Jeff Walters 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

The Bahama Swallow (Tachycineta cyaneoviridis; BAHS) is an endangered species that is endemic to three islands in the northern Bahamas. Very little is known regarding the abundance, distribution or dispersal among islands of BAHS, or the factors responsible for the species’ decline. We are assessing the current population biology of BAHS using population surveys and genetic-based methods, and expanding the limited life history data available by locating and monitoring BAHS nests. Preliminary results show that BAHS breed between April and July, laying an average of three eggs in pre-existing cavities, primarily abandoned woodpecker cavities in snags of Caribbean Pine (Pinus caribaea) and utility poles, and holes in cell phone towers and buildings. Bahamian pine forests were heavily logged through the early 1970s; work to date suggests availability of nest sites limits populations, and reductions in this resource may be responsible for the species’ decline. We are conducting surveys of the pine forest and other habitats to assess the availability of cavity-nesting resources across the landscape and constructing a cavity-nest web illustrating species interactions. BAHS appear to rely on West Indian Woodpeckers (Melanerpes superciliaris) and especially Hairy Woodpeckers (Picoides villosus) to excavate cavities, and compete with secondary cavity-nesters including the American Kestrel (Falco sparverius), La Sagra’s Flycatcher (Myiarchus sagrae), House Sparrow (Passer domesticus) and European Starling (Sturnus vulgaris). By working with local organizations to facilitate and promote this work, our ultimate goal is to provide information that can be used develop conservation strategies for BAHS and their breeding habitat.

River

1st Annual

Interfaces of Global Change Graduate Student Research Symposium

April 21-22, 2016

The first annual Interfaces of Global Change (IGC) Graduate Research Symposium was a great opportunity for IGC Fellows to share their research with the entire global change community at Virginia Tech. The 2-day symposium began on Thursday evening, April 21st, with a special Distinguished Lecture at the Lyric Theatre featuring Dr. Josh Tewksbury, Future Earth. A full slate of events on Friday, April 22nd, provided a forum for students and faculty to interact and explore connections between labs.

During two platform sessions, nine IGC fellows gave oral presentations, and thirteen other students participated in the afternoon poster session. Following a reception for faculty and students attending the symposium, three awards were presented for Best Presentation. First place went to Carl Wepking, a Ph.D. student in biological sciences, who studies how antibiotic use in agricultural livestock affects soil ecosystems. Second place went to Cathy Jachowski, a Ph.D. student in fish and wildlife conservation, who studies the effects of land use and parasitism on hellbender salamanders. Third place was awarded to Ryan McClure, a Ph.D. student in biological sciences, who studies how climate change can impact thermal stratification and oxygenation in reservoirs.

The first place award was named in honor of Dean Karen DePauw, for her role in creating a culture of interdisciplinary graduate education at Virginia Tech. “There’s no more appropriate way to honor the person that has supported the growth and interdisciplinary thinking of our community,” said Bill Hopkins, who is the Director of the Global Change Center and a professor of fish and wildlife conservation in the College of Natural Resources and Environment. “Her vision has facilitated new interactions among faculty and students from different colleges and departments, who are working together to solve complicated problems ranging from obesity and infectious diseases, to water pollution and climate change.”

Congratulations, All!

More photos on the GCC Flicker site!

Poster with face

Detailed AGENDA PDF

Thursday, April 21, 2016

Keynote Lecture:
Dr. Josh Tewksbury, Future Earth
Lyric Theatre, 4:45-5:45 pm
Private reception to follow
~~~~~~~~~~~~~~~~~~~~~~~

Friday, April 22, 2016

8:30 a.m. IGC IGEP Breakfast Forum
with Dr. Josh Tewksbury
Old Guard Dining Room, Preston’s 
Graduate Symposium:
Fralin Hall, 12:00-6:30 pm
11:15 Poster setup
12:15 Posters & Coffee
1:00 Welcome: Dr. Bill Hopkins, Director, Global Change Center
1:05 Opening Remarks: Dr. Karen DePauw, Vice President for Graduate Education and Dean of the Graduate School
1:30 Platform Session 1; Session Chair: Laura Schoenle
2:30 Posters & Coffee
3:00 Platform Session 2; Session Chair: Tamara Fetters
4:15 Poster Reception (students by posters)
6:00 Platform Award Announcements
6:30 Adjourn

All IGC fellows are encouraged to present their work at the symposium. First-year students will give posters on their proposed research/study design; second- and third-year students have the option of presenting either a poster or a talk. Awards will be given for best talks.

Please submit your abstracts to Gloria Schoenholtz (schoeng@vt.edu) by March 28, 2016.  Each abstract should contain 1) Title, 2) Authors and affiliations (e.g., Dept and University), and 3) an abstract not to exceed 250 words in length.

For posters: maximum poster size is 40″ x 60″.  An easel and backboard will be provided.

Comparison of survey techniques on detection probability of northern flying squirrels: Live trapping, camera traps, and ultrasonic acoustics

Authors: Corinne A. Diggins1, L. Michelle Gilley2, Christine A. Kelly3, and W. Mark Ford4

Affiliations: 1. Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 24061 (CAD); 2. Mars Hill University, Mars Hill, NC, 28754 (LGM); 3. North Carolina Wildlife Resources Commission, Asheville, North Carolina, 28806 (CAK); 4. U.S. Geological Survey Virginia Cooperative Fish and Wildlife Research Unit, Blacksburg, Virginia, 24060 (WMF)

The ability to detect a species during surveys or monitoring is important for conservation and management, especially if the species is rare or endangered. Traditional methods can be labor intensive, invasive, and produce low detection rates. Technological advances may provide opportunities to efficiently survey for a species, while reducing field effort. We conducted a comparison study of one traditional technique (live trapping) and two novel non-invasive techniques (camera trapping and ultrasonic acoustic surveys) on detection rates of the Glaucomys sabrinus coloratus at Roan Mountain Highlands in North Carolina. We established three 5 x 5 trapping grids (6.5 ha) with four camera traps and four acoustic detectors systematically embedded in each grid. All three techniques were surveyed simultaneously over two 4-day survey periods. We compared techniques by assessing probability of detection (POD) and latency to detection (LTD), as well as survey effort and cost. Acoustics had the highest POD (0.37±0.06 SE), followed by camera traps (0.30±0.06), and live traps (0.01±0.005). Acoustics had a significantly lower LTD than camera traps (p=0.017), detecting flying squirrels during the first survey night at 75% of survey units. Total field effort was highest with live traps (111.9 hrs) versus acoustics (8.4) and camera traps (9.6), although laboratory effort for data analysis non-invasive techniques made overall effort similar between the three methods. Our study demonstrates that both non-invasive methods are a better rapid-assessment technique of Carolina northern flying squirrel detection compared to live traps. However, protocol for both non-invasive techniques needs further development prior to widespread application.

 

Hypoxia-induced trade-offs on zooplankton vertical distribution and community structure in reservoirs

Authors: Jonathan P. Doubek1, Kevin A. Bierlein2, Alexandra B. Gerling3, Kathleen D. Hamre1, Ryan P. McClure1, Zackary W. Munger4, Cayelan C. Carey1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA; 2. Hydros Consulting Inc., Boulder, CO; 3. American Water Works Association, Denver, CO; 4. Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA

As a result of global change, hypolimnetic hypoxia is increasing in lakes and reservoirs worldwide. Hypoxia can have many detrimental effects on freshwater ecosystem functioning, such as increased internal nutrient and metal loads from bottom sediments. Although the effects of hypoxia on nutrient release has been well-studied, less is known about how hypoxia impacts plankton communities, especially zooplankton. Typically, zooplankton migrate to the dark bottom waters (hypolimnion) during the day to escape visual fish predation in the surface waters (epilimnion). However, due to the physiologically-stressful conditions of hypoxic hypolimnia, zooplankton may remain in the epilimnion during daylight, trading oxic stress for increased predation risk. We sampled five reservoirs weekly to biweekly in southwestern Virginia from May-September 2014 to examine how hypolimnetic oxygen concentrations impact the vertical distribution, abundance, and community composition of zooplankton. These reservoirs varied on a gradient of hypolimnetic oxygen concentrations, from hypoxic to oxic at the sediment-water interface during most of the thermally-stratified period. We also conducted a 36-h sampling campaign on a reservoir with a hypoxic hypolimnion to examine how zooplankton were vertically distributed over an entire day. In hypoxic conditions, zooplankton were predominately found in the epilimnion, and had overall lower abundances than in reservoirs with oxic hypolimnia. Because of the critical role zooplankton play in lakes and reservoirs as the dominant grazers of phytoplankton, it is vitally important to better understand how they may respond to hypoxia, and what the resulting impacts are for lake and reservoir water quality.

 

Variation in thermal tolerance in an invasive lizard (Anolis sagrei)

Authors: Tamara L. Fetters1, William Hopkins1, Joel McGlothlin1

Affiliations: 1. Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Biological invasions allow researchers to assess phenotypic responses to novel environments in a natural setting. Anolis sagrei is a tropical lizard that has successfully invaded geographic ranges with climatic variables that differ substantially from its native range. A climate niche shift in this species has been observed between its native range in the Caribbean and its invasive range in the southeastern United States. This shift is expected to lead to population differences in thermophysiological traits such as thermal tolerance between these two ranges. This study provides data on thermal traits from native and invasive populations of A. sagrei across a latitudinal gradient, and examines how metabolic and locomotive performance varies across different temperatures and populations. In conjunction with previous work on invasive populations of A. sagrei, our results will be important in further understanding the phenotypic adjustments that occur in populations exposed to new environments.

 

Demography of Eastern Hellbenders (Cryptobranchus alleganiensis) Along a Land Use Gradient

Authors: Cathy M. Bodinof Jachowski1 and William A. Hopkins1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Habitat loss due to deforestation is one of the greatest threats to freshwater biodiversity. Many studies have linked land use to changes in abundance and occurrence of freshwater biota. However, few studies have described how land use acts on demographic rates to elicit population level effects. We used mark-recapture data collected between 2007 and 2015 to describe demography of eastern hellbender (Cryptobranchus alleganiensis alleganiensis) populations in six stream reaches stratified across a land use gradient. We tested the hypotheses that loss of forest cover negatively affects hellbender density and population growth rates due to reduced recruitment (evidenced from demographic structure) and/or reduced adult survival. We also investigated relationships between forest cover and potential mechanisms (water quality and substrate) linking land use to hellbender demography. Mean sub-adult/adult densities in 2014-2015 were three- to 9-fold higher in reaches with ≥ 65% forest in riparian areas throughout the catchment relative to reaches with 53-64% forest. Apparent survival of adults did not vary with forest cover. However, population structure reflected a decline in recruitment as riparian forest decreased and populations composed of relatively few (≤ 10% of the population) young adults declined during our study. Water temperature, salinity and predominance of fine substrates increased as riparian forest cover decreased. Our findings suggest hellbender population viability is sensitive to loss of forest cover in riparian areas and that alterations to water quality, substrate or some other correlate of riparian land use acts specifically on demographic rates that determine recruitment to the adult population.

Greenhouse gases respond to whole-ecosystem oxygenation and thermal stratification manipulations in a eutrophic reservoir

Authors: Ryan P. McClure1, Jon P. Doubek1, Kate D. Hamre1, Zack W. Munger1, Barbra R. Niederlehner1, & Cayelan C. Carey1

Affiliations: 1. Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Climate models predict increased air and water temperatures for many regions, thereby increasing the magnitude of freshwater hypoxia and thermal stratification in waterbodies. Simultaneously, the frequency of intense storms is rising, resulting in intermittent periods of oxygenated, mixed conditions and hypoxic, stratified conditions. Changing oxygen concentrations and thermal stratification could significantly alter the production of greenhouse gases, particularly carbon dioxide (CO2) and methane (CH4), and the redox conditions leading to their production in freshwaters. To examine the effects of these climate change impacts, we directly manipulated hypolimnetic oxygen concentrations and thermal stratification at the whole-ecosystem level and explored the responses of carbon dioxide (CO2) and methane (CH4), as well as the electron acceptor pathways that lead to carbon mineralization. We mixed the epilimnion of a small, eutrophic reservoir and intermittently oxygenated the reservoir’s sediments during the summer of 2015. Throughout the summer, we observed dissolved CH4 concentrations ~7500X higher than atmospheric levels. Interestingly, these high CH4 concentrations occurred at the metalimnion during periods of hypolimnetic oxygenation, after epilimnetic mixing events ended. During hypolimnetic oxygenation, CO2 concentrations increased to >13,000 ppm near the sediments, likely due to stimulated aerobic respiration. In the anoxic metalimnion, we observed shifts in the availability of electron acceptors that coincided with the initiation of methanogenesis. Our preliminary data suggest that altered thermal stratification and hypolimnetic oxygen conditions will considerably alter greenhouse gas production in eutrophic reservoirs. Given the global increase in reservoir construction, it is vital that we understand how greenhouse gas production in these ecosystems will respond to a changing climate.

 

Context-dependency of amphibian-Bd-microbiome interactions in the Neotropics: implications for future ecological research and conservation

Authors: Daniel Medina1, Myra Hughey1, Matthew Becker1, Jenifer Walke1, Thomas Umile2, Elizabeth Burzynski2, Anthony Iannetta2, Kevin Minbiole2 and Lisa Belden2

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Chemistry, Villanova University, Villanova, Philadelphia, Pennsylvania

Dramatic declines in amphibian diversity have been documented throughout the Neotropics, in part, due to the skin disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd). Studies suggest that amphibian skin bacterial communities can alter the outcome of the amphibian-Bd interaction, and that Bd might be posing a selective pressure upon these communities in wild populations. However, an understanding of how environmental conditions impact the function of these bacterial communities is scarce. Variable functions of these symbiotic bacteria under different contexts might explain why experiments testing potential amphibian probiotics have obtained mixed results. Given the variation in chytridiomycosis outbreaks across elevations, we aimed to determine how the diversity, structure and function of these symbiotic bacterial communities changes with elevation. We collected skin swab samples in Panamá from three high and three low elevation populations of Silverstoneia flotator. Skin bacterial communities and metabolite profiles were assessed using 16S rRNA gene amplicon sequencing and HPLC-MS, respectively. Our results indicate that across high and low elevations, individuals harbor similar skin bacterial communities, although one lowland site appeared to differ from the others. The metabolite profiles suggest that there is significant variation among frog populations (i.e. sites) and between elevations. Overall, these results suggest that while the frogs have similar bacterial community structure, the local environment might be shaping the metabolites profiles, which indicate a potential functional plasticity that could influence the interaction with Bd. Thus, it is critical to consider the context-dependence of amphibian-microbe-Bd interactions to inform amphibian conservation efforts in the Neotropics.

 

The physiological consequences of infection with Haemosporidian parasites

Authors: Laura Schoenle1, Meredith Kernbach1, Fran Bonier1,2, and Ignacio Moore 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia;  2. Biology Department, Queen’s University, Ontario, Canada

Haemosporidian parasites, including those responsible for avian malaria, can have substantial, negative fitness consequences for their hosts. In areas where the parasites have been recently introduced, infection can be deadly. For example, in Hawaii, malaria has contributed to the extinction of up to twenty species of honeycreeper. Where the parasites are endemic, infection does not appear to have immediate effects, but chronic infection can reduce both annual survival and reproductive success. Although most infected birds experience chronic infections, the effects of long-term exposure to the parasites on host physiology are unknown. We investigated the physiological consequences of infection in adult male red-winged blackbirds (Agelaius phoeniceus) from a population where about 95% of individuals are infected with Haemosporidian parasites. Using both an observational field study and an anti-malarial treatment experiment in an aviary, we examined the effects of Haemosporidian infection on 1) cellular damage, 2) tissue repair, and 3) immune activation. In free living birds, higher parasite burdens were correlated with a decrease in hematocrit and an increase in red blood cell production. The aviary experiment confirmed the relationships found in free-living birds, and additionally showed that infection causes a reduction in mass. We detected no effect of infection on immune function or oxidative damage. The physiological costs of Haemosporidian infection can be substantial and are likely related to the replacement of damaged red blood cells. These results provide a mechanism that could underlie the fitness costs of Haemosporidian infection found in other studies.

 

Understanding the drivers of temporal variation in wood thrush post-fledging survival

Authors: Ben Vernasco1, T. Scott Sillet2, Peter Marra2, and Thomas B. Ryder2

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Migratory Bird Center, Smithsonian Conservation Biology Institute, Washington, D.C.

Between leaving the nest and recruiting into the breeding population the following year, songbirds experience multiple life stages (e.g., post-fledging period, dispersal) with different inherent risks. The post-fledging period is an important period because many songbirds suffer high mortality. Although post-fledgling survival (PFS) has been quantified for a large number of passerines, the drivers of both spatial and temporal variation in survival remain poorly understood. In this study, we used radio telemetry to track fledgling Wood thrush, a declining Neotropical migrant, at 12 sites across 4 years in Southern Indiana. We built competing known-fate survival models to quantify the temporal structure of PFS and to understand which abiotic and biotic factors (i.e., nest parasitism, precipitation and natal habitat characteristics) affect survival probability. Our results show that PFS did not vary within each year (i.e., over the course of the breeding season), but did show substantial variability between years. Models suggest that annual variation in survival is linked to weather, with birds having the lowest survival during droughts. The effect of precipitation deficits showed that young birds that have just fledged the nest are disproportionately impacted in dry years. In contrast, our results did not show a strong effect of either natal habitat characteristics or nest parasitism on survival probability. Overall, this research broadens our understanding of the spatial and temporal drivers of variation in PFS and highlights the impact of region-wide droughts on PFS and subsequent recruitment patterns.

 

Increased antibiotic resistance – effects on microbial communities and ecosystem function

Authors: Carl Wepking1, Bethany Avera2, Brian Badgley3, John E. Barrett1, Josh Franklin1, Katharine F. Knowlton4, Partha P. Ray4, Crystal Smitherman3, Michael S. Strickland1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Ecosystem Science and Sustainability, Colorado State; 3. Department of Crop & Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 4. Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

In the United States nearly 80% of all antibiotics are used in the livestock industry. This use has become a major health concern given the potential for increased antibiotic resistance in human pathogens. While such concerns have obvious human health implications, the impact of increased antibiotic resistance on soil microbial communities and the ecosystem processes they regulate is unknown. At a national scale, we compare soil microbial communities from paired sites receiving either high or low inputs of dairy cattle manure. Given high antibiotic (i.e. cephapirin, a β-lactam antibiotic) excretion rates in manure, we expected that 1) the composition of soil microbial communities, particularly bacteria, would shift toward taxa with demonstrated resistance to these compounds; 2) concentrations of antibiotic resistance genes (ARGs) would increase; and 3) increasing maintenance demands in response to antibiotic additions would lead to decreased microbial efficiency (i.e. greater mass specific respiration). The abundance of the β-lactam resistance gene ampC was 5.2-fold greater in the high input sites, likely due to the use of cephapirin in dairy herds. Additionally, bacterial communities in high input sites differed from those in low input sites, driven primarily by a 25-fold increase in Acinetobacter, an opportunistic pathogen known for β-lactam resistance. Finally, ampC abundance was positively correlated with indicators of microbial stress (i.e. qCO2), and microbial mass specific respiration, which increased 2.1-fold under high inputs. These results demonstrate that antibiotic residues and resistance are not just of human health concern but alter soil microbial communities and the ecosystem processes they regulate.

The Influence of Social Behavior and Stability on Disease Transmission in a Songbird Host

AuthorsMatt Aberle1 and Dana Hawley1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Social interaction in animals has been shown to have lots of fitness benefits, like cooperation in foraging and sharing of resources. However, species that have lots of social interaction are also at a much higher risk of transmitting infectious diseases. Therefore, it is important to study not only social behavior itself, but the structure and stability of social groups as well. Past studies have shown that not only does social stability and behavior change an animal’s exposure to disease, but it can impact physiological factors influencing disease susceptibility through both stress responses and changes in hormones as well. A relatively new method for analyzing social behavior and disease transmission is through contact network modeling. Contact networks show the interactions between individuals within a population and can be created using technology like radio-frequency or GPS. These networks can also give information on how interactions are changing over time as well making them a dynamic tool. Since the early 1990s house finches have been subject to a highly infectious bacterium causing conjunctival pathology. Finches form flocks outside of the breeding season and congregate at bird feeders where the majority of transmission takes place, thus they are an ideal system to test hypotheses relating to social behavior, stability, structure and the impacts of those behaviors on disease transmission. I plan to do my dissertation research on this system utilizing RFID technology placed on feeders to see how manipulations of house finch social behavior and stability affects disease transmission, prevalence, and severity.

 

The Two Towers: An ecosystem story as told by the atmosphere

Authors: Ben Ahlswede1, Quinn Thomas1, Tom O’Halloran1

Affiliations: 1. Department of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

How do we combat climate change? One potential solution is to change our source of energy, from fossil fuels to bio-fuels. Biofuels, have a shorter carbon cycle than fossil fuels, allowing for complete reabsorption of burned fuel within a hundred years as opposed to ten thousand. However, sources of biofuel such as Switchgrass and Loblolly pine have other effects on climate besides absorbing carbon. They also affect the planetary energy balance by altering the reflectivity of the Earth’s surface, and altering how energy is distributed through the atmosphere. These processes have the ability to affect local and regional temperature and can counteract any benefit derived from reduced CO2 in the atmosphere. We have partnered with Sweet Briar College and the Global Change Center to set up two eddy flux covariance systems on the Sweet Briar campus, one over a loblolly stand, and one over a switchgrass field. These paired systems will independently measure fluxes of carbon and water, as well as incoming and outgoing radiation, photosynthetically active radiation, temperature, humidity, precipitation, soil temperature, soil moisture, and energy absorbed by the ground. These measurements will allow us to compare these systems as potential biofuels in a complete accounting of how they affect climate. In addition, data from these towers can be used to inform and constrain future work investigating the effects of implementing a biofuel program on a regional and global scale.

 

Identifying local strains of Nile tilapia Oreochromis niloticus that are adapted to future climate conditions

Authors: Gifty Anane-Taabeah1,2, Emmanuel Frimpong1, Stephen Amisah2, Akwasi Ampofo-Yeboah3, and Eric Hallerman1

Affiliations: 1. Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Fisheries and Watershed Management, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, 3. Department of Fisheries and Aquatic Resources Management, University of Development Studies, Nyankpala Campus, Ghana

This study was conducted to synthesize information on the ambient water quality (temperature, dissolve oxygen and salinity) for the Nile tilapia, an important commercial species, compare wild populations in the Volta basin and the selectively bred Akosombo strain from the basin used in fish farming in Ghana under current and future climate conditions, and develop predictive models delineating the boundaries of the species’ range. A combination of literature survey, field and laboratory methods provided data for meta-analysis, growth and genetic analysis, as well as distribution models. We found variations in water temperature along the latitudinal gradient in Ghana; and temperature was the most informative variable in terms of characterizing the adaptive range and ambient water quality for the species. The results of the growth studies showed no evidence of superior performance of the Akosombo strain over the wild strains under current or predicted future climatic conditions of temperature, dissolved oxygen, or salinity. Significant Fst values from the genetic analysis suggested that the Akosombo strain was well differentiated from all the wild populations (Aframso, Sabare and Binaba) studied. The combined results of the field, growth and genetic studies show that at least one wild population from the Oti River (Sabare) may possess the traits for superior performance under high temperature and low DO conditions. Further studies should concentrate on comparing the Sabare strain with the Akosombo strain under different experimental conditions and increase replications to confirm the suggested differences and the heritability of those performance traits for selective breeding.

 

What’s Bugging the Bugs? Commonalities in Benthic Stressors across the United States

Authors: Heather Govenor1, W. Cully Hession1, Leigh-Anne Krometis1

Affiliations: 1. Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Biological monitoring of invertebrate communities is a key component of stream monitoring under the Clean Water Act in nearly all states, and is one approach used to determine if the biological integrity of state waters is being protected. Monitoring methods, interpretation of field data, and metrics used to evaluate invertebrate communities vary widely across the county, and flexibility in reporting requirements results in inconsistencies in how invertebrate-based impairments are reported to the EPA. Further, states differ in the specific approaches used to determine Total Maximum Daily Loads (TMDLs) to address the stressors associated with impairments. The objective of this research was to determine the pollutants most commonly associated with invertebrate-based stream impairments in the U.S. Through discussions with EPA and state regulators, and evaluation of over 1000 approved TMDL reports written since the initiation of the TMDL program, we confirm a long-thought but formerly undemonstrated assumption that sediment is the most commonly identified stressor associated with invertebrate-based stream impairments nationwide. The variety of approaches used to identify sediment TMDLs are discussed.

 

Millipedes Under Our Feet: Taxonomic Revisions of the Common North American Millipede Genera Pseudopolydesmus(Polydesmida: Polydesmidae) and Nannaria (Polydesmida: Xystodesmidae)

Authors: Derek A. Hennen1 and Paul. E. Marek1

Affiliations: 1. Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Much progress in North American millipede taxonomy has been made over the past three decades, stabilizing nomenclature and providing identification resources. However, much work remains, particularly with regards to alpha-taxonomy and revisions of poorly-understood groups. In eastern North America, the two genera Pseudopolydesmus (Polydesmida: Polydesmidae) and Nannaria (Polydesmida: Xystodesmidae) are among the most commonly encountered millipedes, with 12 and 23 described species, respectively. However, species level classification in Pseudopolydesmus is fuzzy and in need of revision. Nannaria has many undescribed species represented in museum collections, and may even double the number of currently known species. To remedy this, molecular and morphological studies are being conducted to revise the genera and describe new species. Collecting is being done in areas throughout the eastern United States to obtain fresh specimens for molecular analysis and to search for new species, and museum specimens are being examined for morphological analysis. As a result of these studies, photographs and identification keys will be produced, and new species and their ranges will be described.

 

Effects of social environment on the development and maintenance of behavioral strategies for coping with stress.

Authors: Kaan Kerman1 & Kendra Sewall1

Affiliations: 1. Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Coping styles are consistent behavioral differences in how individuals respond to stressful conditions. Proactive individuals are more likely to engage with potential dangers, while reactive individuals tend to avoid a threatening stimuli. Understanding the proximate mechanisms behind these contrasting strategies is an active area of research. In this dissertation project, we will explore one aspect of these proximate processes: mediating role of social environment on the development and expression of coping styles in a model species, the Zebra Finch (Taeniopygia guttata). Using behavioral responses in three different assays to characterize coping styles in our population, we will investigate how exposure to social stress in early development impact the emergence of coping styles later in life, and how social position within a group influence the expression of coping styles in adulthood. We predict that, exposure to stressful social conditions during development, as simulated by artificial injection of stress hormones in egg and hatchling stages (i.e. CORT), causes differential expression of two types of stress hormone receptors in the brain, which leads to a more reactive response later in life. In adulthood, we predict that individuals with strong associations within a flock, and higher dominance status, will be buffered from potential risks in an environment, resulting in a more proactive response even though their coping style is strongly shaped with early life social conditions. This study will have important implications on understanding the emergence of coping with stress as an interplay between epigenetic effects in early life and social conditions in adulthood.

 

Impacts of mining effluent on fishes in the Clinch River and Powell River watersheds

Authors: Zachary Martin1, Serena Ciparis1, Don Orth1, and Paul Angermeier1,2

Affiliations: 1.Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. U.S. Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 

Mining coal in Appalachia has profoundly changed landscapes and impacted >1,900 km of headwater streams. Mining activities can increase instream sedimentation and elevate concentrations of total dissolved solids and trace elements (e.g. selenium) above tolerances of stream fishes. We are evaluating the fish response to mining effluent across a mining-intensity gradient in 16 headwater streams in the upper Powell River and the upper Clinch River watersheds. We expected conductivity, fine sediments, major ion concentrations and [Se] to be elevated in streams on the high-impact end of the gradient. Further, we expected to find fish responses such as shifts in community assemblage, reduced spawning performance, and reduced individual-level health at high-impact sites. Water quality, physical habitat, fish community, and fish tissue samples were collected August – October 2015. There were strong correlations between our mining gradient and measured specific conductivity and concentrations of HCO3–, Ca, Mg, Na, K, and SO42-. Seventeen fish species were collected and individual-fish data were gathered on two species, Etheostoma flabellare and Rhinichthys obtusus. A hierarchical cluster analysis characterizing species composition at sites identified two groups: widespread species (Campostoma anomalumRhinichthys obtususEtheostoma flabellare, and Semotilus atromaculatus) and patchily distributed species (all others). Although E. flabellare was widespread, it was absent from assemblages at four high-impact sites. Future interpretation of community data will be paired with physical habitat and water quality data. This spring we are also processing fish tissue samples to describe changes in individual-level health and conducting spawning surveys of E. flabellare across our mining-impact gradient.

 

Behavior and Impact of Spathius galinae and Spathius agrili on Emerald Ash Borer in Virginia

Authors: Max Ragozzino1, Scott Salom1

Affiliations: 1. Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Emerald ash borer (EAB), Agrilus planipennis Fairemaire (Coleoptera: Buprestidae) is a wood-boring beetle native to Asia introduced to Michigan in 2002. In both its native range and in North America, EAB primarily feeds on ash trees (Fraxinus sp.). In North America, ash tree stands suffer complete mortality within 6 years of infestation, and it is estimated to kill 38 million ash trees by 2019. EAB larvae are frequently predated by native woodpeckers (Picidae), accounting for up to 39% of all EAB larvae in some areas. Four hymenopteran parasitoids have been identified in Asia and introduced to the U.S. as biological control agents against EAB. This study will focus on two larval parasitoids, Spathius agrili Yang (Hymenoptera: Braconidae), and Spathius galinae Belokobylskij and Strazenac (Hymenoptera: Braconidae). Neither parasitoid is established in Virginia. We plan to study competitive interactions between both parasitoid species, including multiparasitism and adult competition to determine the best course of action for establishment. We will release both parasitoids across Virginia at a variety of ash dense forest locations, and monitor their activity using a variety of methods including sentinel logs and total larval counts. Once establishment occurs, we will exclude woodpeckers from infested ash trees in order to determine the effect of woodpecker predation on the parasitoids.

 

Climate Change, Coups, and Critically Endangered Species: First Aerial Drone Surveys of Madagascar’s Lemurs

AuthorsBrandon P Semel and Sarah M Karpanty

Affiliations: Fish and Wildlife Conservation Department, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Lemurs are found only in Madagascar and are earth’s most threatened mammals. Hunting, habitat loss, government instability, and climate change all pose serious threats to lemur species. Establishing baseline population estimates and enacting long-term population and habitat monitoring efforts to guide conservation strategies are critical to their survival. However, traditional survey methods are labor intensive, expensive, and can facilitate resource extraction. Novel technologies, such as aerial drones, will help to overcome these obstacles. Population estimates and threat quantification for diurnal species in northern Madagascar will be obtained summer 2016, including critically endangered golden-crowned sifakas (Propithecus tattersalli) and endangered crowned (Eulemur coronatus) and Sanford’s brown (E. sanfordi) lemurs. Prior to conducting drone surveys, lemur behavioral responses to their presence will be assessed so that surveys are performed in a way that minimizes animal stress. A cost-benefit analysis comparing line transects and aerial drone surveys will be conducted, fragments with extirpated lemur populations will be identified for future translocation, and land cover change will be mapped to aid in conservation prioritization and to establish a habitat baseline for future climate change studies. Partnering with Malagasy conservation initiatives will ensure continued long-term monitoring. Pilot data will facilitate my doctoral work investigating how lemurs in this region will respond to climate change-induced environmental change and aid in local conservation efforts in a global biodiversity hotspot. Results will be broadly applicable to wildlife management and conservation around the world.

 

Modeling Freshwater Salinity for Aquatic Biodiversity Management

Authors: Tony Timpano1, Stephen Schoenholtz1, David Soucek2, and Carl Zipper3

Affiliations: 1. Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Illinois Natural History Survey, U. Illinois Urbana-Champaign; 3. Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Human activities like agriculture and resource extraction can increase the dissolved inorganic ion concentration (i.e., salinity) in waterbodies, creating toxic conditions for life adapted to dilute freshwater. This salinization of freshwaters is a global threat to aquatic biodiversity. In the USA, mountaintop coal mining contributes to salinization of headwater streams in the Appalachian region, a biodiversity hotspot. Recently, water quality managers have sought to mitigate the biotic effects of salinization by determining the limits of salinity tolerable to freshwater organisms. To date, limits have been based on salinity-biota relationships observed in field surveys that measured salinity only once per year. However, because salinity can vary with seasonal stream flow, effective management will require understanding the temporal patterns. Toward that end, we measured the salinity surrogate electrical conductivity continuously for three years in 25 minimally-disturbed headwater streams across a gradient of salinity in the Appalachian coalfields of Virginia and West Virginia. We found that salinity changed throughout the year, in a distinct seasonal pattern in nearly all streams, regardless of mean annual salinity level. We modeled the pattern using a sine-cosine linear model and found moderate to strong fits. The models indicated that annual minimum salinity occurred in spring and annual maximum salinity occurred in autumn. Averaged across all sites, seasonal deviations from mean annual salinity reached approximately 20% in spring and autumn. Our models indicate substantial, yet predictable seasonal variation in salinity, which should improve salinity management to achieve aquatic biodiversity goals.

 

Subtle variation in incubation temperature may have long-term effects on immune function and sexually-selected traits of an altricial model, the zebra finch

AuthorsJ. Wagner1, M. Beck2, E. Joseck3, W. Hopkins1

Affiliations: 1. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 2. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; 3. Department of Animal and Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Avian incubation temperature plays an important role in offspring development and is affected by the interaction between parental behavior and environmental variables. Numerous studies have indicated its importance to a suite of phenotypic traits in offspring, yet we have a fairly limited understanding of how variation in incubation temperature affects individuals throughout adulthood. The literature has identified numerous traits that are affected in altricial nestlings prior to fledging and in precocial birds (chickens and ducks), but whether or not incubation temperature has long-lasting impacts on individuals, possibly affecting their lifetime phenotypic trajectory, is unknown.  We investigated how growth, immune function, and ornamental plumage was influenced by variation in incubation temperature by incubating eggs at two biologically-relevant temperatures (36.5 and 37.5°C) and measuring endpoints on nestlings and adults. We found no differences in growth or immune function in young birds across the two incubation temperatures. However, compared with 37.5°C individuals, those incubated at 36.5°C had a lower cell-mediated immune response as adults (40 days post-hatch) and males had lower brightness and intensity ornamental plumage coloration at sexual maturity (~100 days post-hatch). This study demonstrates how subtle differences in the conditions experienced during embryonic development may have a crucial and long-lasting influence on individual phenotype.

 

A Comparison of Intraspecific Aggression in Populations of the Lizard, Anolis sagrei, at Varying Stages of Species Invasion

Authors: Julie M. Wiemerslage1 and Joel McGlothlin1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

It is important to asses how invasive species are able to thrive in novel environments in order to predict and prevent future invasions. Additionally, the study of invasive species allows a unique opportunity to assess how species adapt to novel conditions, which are often created by current global changes. Invasive species often undergo phenotypic divergence from their native counterparts because they must adjust to novel conditions to persist outside of their native range. Behavior is a key determinant of success for invasive animals because it can facilitate rapid responses to novel conditions, so it is likely that behavioral divergence occurs in species invasions. Anolis sagrei is an invasive territorial lizard in the Southeast United States that is native to the Caribbean. For A. sagrei and other territorial species, increased territorial aggression may be selected for when their ranges expand into areas that contain closely related species. This study investigates the differences in aggressive behavior between populations of A. sagrei at different stages of invasion. One-on-one aggressive encounters were staged between males in order to assess differences in aggressive behavior between different populations. We had two competing hypotheses: 1. lizards at the front of the range are more aggressive than other populations because aggression allows them to outcompete species in their new range, and 2. lizards at the front of the range are less aggressive than other populations because there is lower population density there, thus less competition.

 

Population biology, life history, and ecology of the Bahama Swallow (Tachycineta cyaneoviridis): informing conservation of an endangered bird in the northern Bahamas

Authors: Maya Wilson1 and Jeffrey Walters1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

The Bahama Swallow (Tachycineta cyaneoviridis) is an endangered bird species that is endemic to the northern Bahamas. This doctoral research project focuses on three central questions:

  • What are the features of the current Bahama Swallow population biology? Available population estimates indicate a sharp decline in population abundance, and there is currently no information regarding distribution and dispersal. I am conducting surveys and using capture-recapture to estimate abundance and distribution, and taking genetic samples to assess the dispersal of populations between islands.
  • What are the life history characteristics of the Bahama Swallow? The life history data for this species are limited, and I am expanding these data by monitoring active nests during several consecutive breeding seasons.
  • What are the potential agents of decline of Bahama Swallow populations? (A) Habitat loss and degradation: Bahamian pine forests were heavily logged, and continued loss and degradation of pine forests poses an ongoing threat. I am conducting habitat surveys to assess the availability of suitable breeding habitat. (B) Competition for nesting cavities: The Bahama Swallow may face competition for cavities with other cavity-nesting bird species. I am identifying the species that excavate and utilize the same types of nesting cavities as Bahama Swallows, and designing a cavity nest web illustrating the interactions of these species. (C) Predation: Increased abundance of nest predators could pose a threat to the Bahama Swallow. I am monitoring active nests to determine whether the rates of depredation are sufficiently high to contribute significantly to population declines.

 

Life history and ecology of the endangered Bahama Swallow (Tachycineta cyaneoviridis)

Authors: Maya Wilson 1 and Dr. Jeff Walters 1

Affiliations: 1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

The Bahama Swallow (Tachycineta cyaneoviridis; BAHS) is an endangered species that is endemic to three islands in the northern Bahamas. Very little is known regarding the abundance, distribution or dispersal among islands of BAHS, or the factors responsible for the species’ decline. We are assessing the current population biology of BAHS using population surveys and genetic-based methods, and expanding the limited life history data available by locating and monitoring BAHS nests. Preliminary results show that BAHS breed between April and July, laying an average of three eggs in pre-existing cavities, primarily abandoned woodpecker cavities in snags of Caribbean Pine (Pinus caribaea) and utility poles, and holes in cell phone towers and buildings. Bahamian pine forests were heavily logged through the early 1970s; work to date suggests availability of nest sites limits populations, and reductions in this resource may be responsible for the species’ decline. We are conducting surveys of the pine forest and other habitats to assess the availability of cavity-nesting resources across the landscape and constructing a cavity-nest web illustrating species interactions. BAHS appear to rely on West Indian Woodpeckers (Melanerpes superciliaris) and especially Hairy Woodpeckers (Picoides villosus) to excavate cavities, and compete with secondary cavity-nesters including the American Kestrel (Falco sparverius), La Sagra’s Flycatcher (Myiarchus sagrae), House Sparrow (Passer domesticus) and European Starling (Sturnus vulgaris). By working with local organizations to facilitate and promote this work, our ultimate goal is to provide information that can be used develop conservation strategies for BAHS and their breeding habitat.