Digital Commons Network^™

Landscape Ecology And Conservation Of Freshwater Turtles Across The Eastern United States, H. Patrick Roberts

Doctoral Dissertations

Space use and movement patterns are integral to population dynamics and are often indicative of vulnerability to anthropogenic threats. Spatial ecology research can be fundamental to conservation strategies but is largely biased toward short-term intra- and interannual patterns. Without an understanding of space use over temporal scales commensurate with lifespan and the processes that may influence movement, conservation tools derived from short-term (2–4 yrs) movement patterns may be misguided or ineffective, particularly for long-lived species. The goal of Chapter 1 was to characterize the long-term (multi-decadal) spatial ecology of three long-lived (80–110 yrs) turtle species. We revisited six areas where …

Habitat Use And Individual-Based Modeling Of Bald Eagles In Maine Near Current And Potential Wind Energy Facilities, Blake Massey

Doctoral Dissertations

Wind energy facilitates have expanded significantly in the United States over the last few decades due to technological advancements, regulatory incentives, and policies aimed at increasing renewable energy production, but poorly sited turbines may have adverse effects on local and migratory birds, bats, and other wildlife and their habitats. In the northeastern United States, Maine has become the leader in wind energy but also has the greatest density of Bald Eagles in the region. As wind energy production continues to be developed across the state and in coastal waters, research is needed to analyze and assess potential risks, including displacement, …

Monitoring Mammals At Multiple Scales: Case Studies From Carnivore Communities, Kadambari Devarajan

Doctoral Dissertations

Carnivores are distributed widely and threatened by habitat loss, poaching, climate change, and disease. They are considered integral to ecosystem function through their direct and indirect interactions with species at different trophic levels. Given the importance of carnivores, it is of high conservation priority to understand the processes driving carnivore assemblages in different systems. It is thus essential to determine the abiotic and biotic drivers of carnivore community composition at different spatial scales and address the following questions: (i) What factors influence carnivore community composition and diversity? (ii) How do the factors influencing carnivore communities vary across spatial and temporal …

The Effects Of Urbanization On The Avian Gut Microbiome, Mae Berlow

Doctoral Dissertations

The gut microbiome influences and is influenced by the host, and can affect the host organism by contributing to health, development and immunity. Similarly, the host can influence this community; it’s makeup can vary with host species, locality, diet, social stressors, and environmental stressors. Some of these environmental stressors have arisen due to human-induced rapid environmental change, like urbanization. The physiology and behaviors of organisms that are able to persist in urban environments are often different from their non-urban congeners. Nutrition, development, and immunity—all of which are affected by the gut microbiome—are important factors that can determine survival in urban …

Evolution And Resurrection Ecology Of A Foundational Coastal Marsh Plant, Jennifer L. Summers

Doctoral Dissertations

Stratified storage of dormant seeds in soil can result in natural archives useful for studying evolutionary responses to environmental change. However, few studies leverage soil-stored seed banks as natural archives, in part because of concerns over attrition, bias, and sediment mixing. Here, I examine the persistent seed bank of Schoenoplectus americanus, a foundational brackish marsh sedge, to a) determine whether it can serve as a resource for reconstructing demographic and population genetic/genomic variation, b) whether and how evolution may be occurring across a century. After extracting seeds from radionuclide-dated soil cores taken across the Chesapeake Bay, I “resurrected” age …

Fear, Parental Behavior, And Community Structure In Residential Lands, Aaron M. Grade

Doctoral Dissertations

In an urbanizing world, residential lands present an opportunity for conservation of biodiversity right in our backyards. Informed conservation necessitates a mechanistic understanding of how development influences animal populations and communities. Birds nesting in residential lands are less productive in urban yards than rural yards. Urban yards also have higher densities of potential predators, but lower per capita predation, indicating that direct predation is not entirely responsible for lack of productivity. I suggest that fear effects, also known as non-lethal effects, could be a mechanism by which predators exert indirect influence on bird parental behavior and nestling condition in urban …

Connecting The Social And Spatial Behaviors Of A Territorial Species (Anolis Carolinensis), Jordan M. Bush

Doctoral Dissertations

Why animals live where they do is a key question in ecology and evolution. An individual’s home range determines the resources they have access to, conspecifics they encounter, and predators and pitfalls they must avoid. Home range behaviors also have an inherently social component; where animals live affects the rivals they compete with and the mates they have access to. This is especially true in territorial species, as defensive displays make up a large portion of their social behaviors. In this dissertation, I sought to understand how territorial behaviors affect the social lives of the green anole lizard (Anolis …

The Effects Of Anthropogenic Stress On Nitrogen-Cycling Microbial Communities In Temperate And Tropical Soils, George S. Hamaoui Jr.

Doctoral Dissertations

In this dissertation several research studies are discussed that characterize the effects of anthropogenic, or human-induced, stress on both ammonia-oxidizing and total bacterial soil microbial communities. The disturbances of land-use change in tropical, South American rainforests and artificial warming and nitrogen (N) fertilization in temperate, North American forests were investigated as these disturbances represent past and current disturbances caused by human landscape alteration and climate change. Initially, the response of soil ammonia-oxidizing microbial communities to land-use change from primary rainforest to pasture and, finally, back to secondary forest was determined. Next, these analyses of land-use change effects were expanded to …

Assessing The Functional Similarity Of Native And Invasive Anolis Lizards In The Food Webs Of Structurally-Simple Habitats In Florida, Nathan W. Turnbough

Doctoral Dissertations

Invasive species often displace ecologically-similar native species, but the extent to which invading and displaced species function similarly in the food web processes of invaded communities is largely unknown. I investigated whether populations and individuals of an invasive Anolis lizard (the brown anole, Anolis sagrei) and the native congener it displaces in Florida (the green anole, Anolis carolinensis) are functionally equivalent in the food webs of open and structurally-simple habitats. In a system of invaded and uninvaded dredge-spoils islands, I found that both arthropod communities and winter bird communities covaried with brown anole abundance (and therefore the identity …

Individual Variation In Plant Traits Drives Species Interactions, Ecosystem Functioning, And Responses To Global Change, Quentin Daniel Read

Doctoral Dissertations

Ecologists have long sought to understand the processes that lead to the riotous diversity in communities of organisms that inhabit disparate climates and landscapes. Such a diversity of traits leads to a diversity of interactions among species in natural communities, which in turn generates a diversity of potential responses to ongoing global change. In this dissertation, I do three things: I explore the forces that structure plant communities and the ecosystem functions that they mediate, I describe patterns of variation among communities, species, and individual organisms across environmental contexts, and I disentangle the direct effects of global change from the …

Integrated Modeling Of Land Use And Climate Change Impacts On Multiscale Ecosystems Of Central African Watersheds, Simon Nampindo

Doctoral Dissertations

Assessment and management of ecosystem services demands diverse knowledge of the system components. Land use change occurring mainly through deforestation, expansion of agriculture and unregulated extraction of natural resources are the greatest challenges of the Congo basin and yet is central to supporting over 100 million people. This study undertook to implement an integrated modeling of multiscale ecosystems of central African watersheds and model the impact of anthropogenic factors on elephant population in Greater Virunga landscape. The study was conducted at varied scales, regional, landscape, and community. Regional study included watershed analysis and hydrological assessment using remotely sensed data implemented …

Impacts And Implications Of Co-Occurring Invasive Plant Species, Sara Elizabeth Kuebbing

Doctoral Dissertations

The anthropogenic spread of species is a potent form of global change that impacts the population dynamics of native species, the composition of native communities, and the functioning of ecosystems. As the reorganization of species around the globe continues unabated, there is an increasing likelihood that habitats will contain co-occurring invaders. In this dissertation, I emphasize the need to study co-occurring invasive plants by juxtaposing the relative occurrence of multiple versus single invasive plants in important conservation habitats to the relative occurrence of published studies that consider the impacts of single versus multiple invasive plants. I found that over two-thirds …

Wood Decomposition In A Warmer World, Emily Elizabeth Austin

Doctoral Dissertations

Climatic warming is altering species distributions and ecosystem functions across the globe. Wood is an important carbon pool and the fungal communities in wood are relatively simple compared to those in soil. These factors make decomposing wood an ideal system for exploring the influence of decomposer community on the response of decomposition to warming. My research has focused on the effects of warming wood decomposition rates and wood decomposing communities. Using field and lab- based manipulative experiments and field observations I explore the influence of tree species, wood decomposition stage, geography and warming on fungal community structure and activity. In …

Ant Community Dynamics And The Effects Of Global Warming, Katharine Lisa Stuble

Doctoral Dissertations

This dissertation seeks to provide an understanding of how species coexist and, further, how climate change may alter communities by acting on the mechanisms that promote coexistence. Specifically, I examined coexistence among ant species in eastern deciduous forests and the effects that warming may have on foraging activity. Through a series of field observations, I sought evidence for the importance of four of the most commonly cited mechanisms for coexistence among ant species: the dominance – discovery tradeoff, the dominance – thermal tolerance tradeoff, spatial segregation, and niche partitioning. In this system, I did not find evidence for any of …

Evolutionary Interactions In Invasive Species: The Importance Of Plant-Soil Feedbacks To Local Adaptation And Rapid Evolution, Emmi Felker-Quinn

Doctoral Dissertations

Interactions between intraspecific plant variation and the environment can create evolutionary and ecosystem feedbacks, but the contribution of these feedbacks to the success of invasive plant species has rarely been explored or quantified. To test whether evolution occurs during the process of plant invasion I conducted three major experiments and a meta-analysis to test various aspects of this central question. First, I conducted a meta-analysis of studies that tested the Evolution of Increased Competitive Ability (EICA) hypothesis. The meta-analysis did not support EICA’s prediction that release from herbivores leads to reduced defenses and higher performance, but it showed that evolutionary …

Multiple Responses By Cerulean Warblers To Experimental Forest Disturbance In The Appalachian Mountains, Than James Boves

Doctoral Dissertations

The Cerulean Warbler (Setophaga cerulea) is a mature forest obligate and one of the fastest declining songbird species in the United States. This decline may be related to a lack of disturbance within contemporary forests; however, the consequences of disturbance on the species have not been rigorously evaluated. Thus, we assessed multiple responses by Cerulean Warblers to a range of experimental forest disturbances across the core of their breeding range in the Appalachian Mountains. We quantified individual and population responses to these manipulations, and assessed the potential consequences of disturbance on the sexual signaling system. Male ceruleans were …

Evolution, Speciation, And Conservation Of Amblyopsid Cavefishes, Matthew Lance Niemiller

Doctoral Dissertations

Cave organisms are classic examples of regressive evolution, as many disparate taxa have evolved similar convergent phenotypes in subterranean environments. While recent phylogeographic and population genetic analyses have greatly improved our understanding of the evolutionary and biogeographic history of cave organisms, many questions remain unanswered or poorly investigated. I investigated several evolutionary and biogeographic questions in a model system for regressive evolution and studies of ecological and evolutionary mechanisms, amblyopsid cavefishes. In chapter I, I used recently developed methods to delimit species boundaries and relationships in a widely distributed cavefish, Typhlichthys. I show that species diversity in Typhlichthys is …

Adiposity Related Protection Of Intestinal Tumorigenesis: Interaction With Dietary Calcium, Shengli Ding

Doctoral Dissertations

Excess adipose tissue is a risk factor for developing colorectal cancer. However, the present studies demonstrate that lack of adipose-derived factor(s), such as adiponectin, due to the substantial loss of body fat on high dairy calcium diet could increase susceptibility to intestinal tumorigenesis. These studies suggest that a minimum amount or threshold level of adipose tissue may be required to significantly attenuate tumorigenesis.

In Apc^Min/+ mice, consumption of high dairy calcium diet exhibited markedly reduced adipose tissue and increased tumor number. Our results showed that the high calcium diet reduced fat pad mass by 65%-82% in Apc^Min/+ (p …

Scale And Contingency In Plant Demography: Quantitative Approaches And Inference, Sean Maurice Mcmahon

Doctoral Dissertations

Ecologists have long recognized that patterns measured in nature often depend upon the context in which they are observed and the scale at which they are observed. When studying plant populations, the role of scale and contingency becomes crucial. Thinking about a plant community as a system is essential as populations of plants are centered within a network that influences their dynamics in direct and indirect ways. Plant populations are inherently scale-dependent because they have properties as a group that can be independent of their properties as individual stems. Although the challenge of interpreting population patterns in the face of …

The Tangled Web Of Community Ecology: Making Sense Of Complex Data, Monica Lynn Beals

Doctoral Dissertations

Ecological communities are governed by complicated processes that give rise to observable patterns. Making sense of these patterns, much less inferring the underlying processes, has proved challenging for several reasons. Manipulative experiments in natural communities may not be feasible due to large numbers of variables, lack of adequate replication, or the risk of undesirable consequences (e.g., introducing an invasive species). The multivariate nature of ecological datasets presents analytical problems as well; many statistical techniques familiar to ecologists have difficulty handling large numbers of potentially collinear variables. I present results from three studies of spider communities in which I employ a …

A Biogeographic Study Of Amphibians In Tennessee, William H. Redmond Jr.

Doctoral Dissertations

Range maps and descriptive, taxonomic, and habitat information are provided for 20 species of frogs and 41 species of salamanders. The environmental setting of Tennessee is described in terms of geology, physiography, climate, drainages, soils, vegetation, and ecoregions. For the purposes of the analyses, a grid cell pattern containing 122 sampling units is used, and the amphibian fauna is organized into three faunal groups. These groups are frog species, salamander species, and all species grouped together as amphibians. The results of a G-test for the frequency distribution of range limits fitted to a Poisson distribution suggest a clumped dispersion pattern …