Wildlife biodiversity provides a variety of ecosystem services and is an important indicator of overall ecosystem health. This research investigates the relationship between wildlife biodiversity and landscape characteristics in Virginia. The goal is to produce predictive models of biodiversity within the Commonwealth using environmental characteristics, including fragmentation metrics at the class- and landscape-levels, as well as other environmental variables. The 1248 12-digit watersheds in Virginia are the sampling units for the analyses, with the state stratified into the seven US Environmental Protection Agency's Level III classification. Data on wildlife alpha diversity is based on two sets of species data maintained by the Virginia Dept. of Game & Inland Fisheries (VDGIF). The first chapter provides an introduction to the issue of biodiversity conservation and the background information for this work. The second chapter describes the study using the 2001 National Land Cover Data to calculate class- and landscape-level fragmentation metrics. Best subset regression is used to determine the best predictors for wildlife biodiversity using these metrics. Final selected models range in predictive power from R2 = 0.41 to 0.73 for each of the 7 ecoregions. The third chapter analyzes the relationship between wildlife biodiversity and various environmental variables in order to determine the strength of these factors as drivers for alpha diversity. These variables are then incorporated with the fragmentation metrics in an attempt to improve the biodiversity models. The environmental variable models had R2 = 0.22 to 0.65 across the ecoregions, while R2 = 0.28 to 0.72 when the environmental and fragmentation variables are combined. The last chapter focuses on the conclusions of the studies, the limitations of the data, and the benefits of this work. Overall, our results underline the importance of using fragmentation metrics in Virginia's wildlife models. / Master of Science

Cultivation of marine ecosystems began in the early Holocene and has contributed vital resources to humans over millennia. Several more recent cultivation practices, however, erode biodiversity. Emerging lines of evidence indicate that certain resource management practices may promote favourable ecological conditions. Here, I use the co-occurrence of 24 First Nations clam gardens, shellfish aquaculture farms, and unmodified clam beaches to test several hypotheses concerning the ecological implications of managing intertidal bivalve populations. To so do, in 2015 and 2016, I surveyed epifaunal (surface) and bivalve communities and quantified each intertidal sites’ abiotic conditions, including sediment characteristics and substrate composition. In 2017, I generated three-dimensional models of each site using structure-from-motion photogrammetry and measured several aspects of habitat complexity. Statistical analyses use a combination of non-parametric multivariate statistics, multivariate regression trees, and random forests to quantify the extent to which the intertidal resource cultivation structures nearshore biodiversity Chapter 1 outlines a brief history of humanity's use of marine resources, the transition from extracting to cultivating aquatic taxa, and the emergences of the northeast Pacific’s most prevalent shellfish cultivation practices: clam gardens and shellfish farms. Chapter 2 evaluates the ability of epifaunal community assessment methods to capture species diversity by conducting a paired field experiment using four assessment methods: photo-quadrat, point-intercept, random subsampling, and full-quadrat assessments. Conducting each method concurrently within multiple intertidal sites allowed me to quantify the implications of varying sampling areas, subsampling, and photo surveys on detecting species diversity, abundance, and sample- and coverage-based biodiversity metrics. Species richness, density, and sample-based rarefaction varied between methods, despite assessments occurring at the same locations, with photo-quadrats detecting the lowest estimates and full-quadrat assessments the highest. Abundance estimates were consistent among methods, supporting the use of extrapolation. Coverage-based rarefaction and extrapolation curves confirmed that these dissimilarities were due to differences between the methods, not the sample completeness. The top-performing method, random subsampling, was used to conduct Chapter 4’s surveys. Chapter 3 examines the connection between shellfish biomass and the ecological conditions clam garden and shellfish farms foster. First, I established the methodological implications of varying sediment volume on the detection of bivalve diversity, abundance, shell length, and sample- and coverage-based biodiversity metrics. Similar to Chapter 2, this examination identified the most suitable method, which I used during the 2015 and 2016 bivalve surveys. The analyses quantified several interactions between each sites’ abiotic conditions and biological communities including, the influence of substrate composition, sediment characteristics, and physical complexity on bivalve communities, and if bivalve richness and habitat complexity facilitates increases in bivalve biomass. Chapter 4 quantifies the extent to which managing intertidal bivalves enhance habitat complexity, fostering increased diversity in the epifaunal communities. This chapter combines 2015, 2016, and 2017 surveys of the sites' epifaunal communities and habitat complexity metrics, including fractal dimension at four-resolutions and linear rugosity. Clam gardens enhance fine- and broad-scale complexity, while shellfish farms primarily increase fine-scale complexity, allowing for insights into parallel and divergent community responses. Chapter 5 presents an overview of shellfish as a marine subsidy to coastal terrestrial ecosystems along the Pacific coast of North America. I identified the vectors that transport shellfish-derived nutrients into coastal terrestrial environments, including birds, mammals, and over 13,000 years of marine resource use by local people. I also examined the abundance of shellfish-derived nutrients transported, the prolonged persistence of shellfish subsidies once deposited within terrestrial ecosystems, and the ecological implications for recipient ecosystems. Chapter 6 contextualizes the preceding chapters relative to the broader literature. The objective is to provide insight into how multiple shellfish cultivation systems influence biological communities, how ecological mechanisms facilitate biotic responses, and summarize the implications for conservation planning, Indigenous resource sovereignty, and biodiversity preservation. It also explores future work, specifically the need to support efforts that pair Indigenous knowledge, and ways of knowing with Western scientific insights to address conservation challenges. / Graduate / 2022-12-13

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One of the three largest systems of black-tailed prairie dog (BTPD) colonies is located in northwestern Chihuahua, Mexico. During the last two decades, the area occupied by these colonies has been highly reduced and fragmented. Previous studies suggested that agriculture, poisoning, cattle overgrazing and shrub encroachment could be the factors responsible for such declines. However, the severe drought occurring in the region between 1994 and 2004 has not been considered in this equation. Because these populations occur in arid regions at the southern edge of the species range, they could be especially sensitive to changes in plant productivity. Furthermore, fragmentation of colonies may accelerate population declines due to size and isolation effects. In this study, I analyzed species-habitat relationships at different spatial and temporal scales to understand the causes of recent declines of BTPDs in northwestern Chihuahua. The most severe loss of colony area and most local extinctions occurred between 1988 and 2000, but most likely before 1997. Extinction of colonies before 2000 mostly occurred at small and isolated colonies in low-productivity areas. The coincidence of greatest area decline with the occurrence of most intense drought suggests a prominent role of drought in the population collapse. Overall, patterns of BTPD occurrence and abundance in Chihuahua are greatly influenced by spatial and temporal variation in forage cover. Although BTPDs were more likely to occur in open areas with short vegetation, increased forage cover positively predicted occurrence. High levels of forage cover during the dry season were positively related with BTPD density, juvenile production and population rate of change, but forage cover during the preceding rainy season was a negative predictor of demographic indices. High plant productivity during humid periods seems to have negative impacts on BTPD populations, presumably because the rapid plant growth reduces visibility and predator detection by BTPDs. The most influential landscape variable was the effective isolation of colonies. Although increased isolation may reduce the probability of occurrence at a given site, highly isolated locations may support high population densities. Contrary to my original predictions, I did not detect significant impacts of human-related factors on BTPD distribution and abundance. / Ecology