Graduate Symposium 2021 Abstracts
All IGC fellows will have the opportunity to present their work as part of the symposium, although a limited number of presentations will be built in to the symposium schedule due to time constraints. All presentations will be available to IGC fellows and GCC faculty to view online through May 30, 2021.
There will be three presentation opportunities as part of the virtual symposium:
- Platform presentations –
- 10 to 12 platform presentations focused on research/study results
- Presentations will be pre-recorded (12-minute max), followed by 3 min for live Q&A
- Preference is given to IGC fellows reporting on global-change related research in their 3rd, 4th or 5th year of study
- Research power talks–
- Pre-recorded presentations (3-minute max), followed by 2 min for live Q&A
- 12 research focused power talks will be selected to feature during the symposium on April 23rd
- All 2nd – 5th year fellows are encouraged to practice their scientific communication skills and submit a research power talk! All power talks will be available for the GCC community to view online through May 30, 2021
- New IGC fellows power talks –
- The Spring 2021 cohort of new IGC fellows are invited and strongly encouraged to share brief introductions about yourself and your research interests to the rest of the GCC & IGC community.
- Pre-recorded presentations (90-second max)
- Fellows are encouraged to have fun with these: help us get to know you and give us a glimpse of your personality and passions!
Awards will be given for best talks in both the platform presentation and research power talks categories.
All presentations will be pre-recorded. Directions and guidance for how to record videos will be provided.
Friday, April 23, 2021
9:00 – 9:15 am Welcome, by GCC & IGC Director Dr. Bill Hopkins
9:15 – 10:15 am IGC Platform Presentations Session 1
10:15 – 10:30 am Break
10:30 – 11:30 am IGC Platform Presentations Session 2
11:30 am – 12:30 pm Break
12:30 – 1:30 pm IGC Platform Presentations Session 3
1:30 – 2:00 pm Break
2:00 – 3:00 pm Power Talks: Research
3:00 – 3:30 pm Break
3:30 – 3:50 pm Power Talks: Meet the newest IGC Fellows
3:50 – 4:05 pm IGC Peer Mentoring Program Overview
4:05 – 4:30 pm Best Presentation Awards Announcement
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
RESEARCH POWER TALKS
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.
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.
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.
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.
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.
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.
Affiliations: 1Department of Biomedical Sciences and Pathobiology, VA-MD College of Veterinary Medicine; 2Department of Animal and Poultry Sciences, Virginia Tech
Usutu virus (USUV; Flavivirus), 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.
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.
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 effectivity. We 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.