Life Sciences Commons^™

A Systematic And Biogeographic Study Of Trillium (Melanthiaceae), Jayne A. Lampley

Doctoral Dissertations

Trillium (Melanthiaceae, Parideae) has a disjunct distribution occurring in eastern and western North America, and eastern Asia. Past studies have examined the phylogeny and historical biogeography of Melanthiaceae and Parideae, however these studies either did not fully examine these aspects within Trillium or did not employ sufficiently broad taxonomic or character sampling to clarify relationships among taxa. The first phylogenetic analysis presented in this study provides a resolved phylogeny for Trillium s.l. and Paris s.l. by using a dataset of 70 plastid coding genes and by sampling broadly from Trillium s.s., Pseudotrillium, Trillidium, Paris s.s., Daiswa, and Kinugasa. The results …

Geographic Patterns Of Genetic Diversity Under Climate Change: Linking Genes And Ecosystems, Shannon L. Bayliss

Doctoral Dissertations

Climate change is having profound effects on species distributions. However, much less is understood about how climate change may alter the distribution of genetic variation within species across landscapes. Maintaining genetic diversity within populations is essential for the survival of species in the face of rapid climatic changes, but importantly, losses of genetic variation will also have significant consequences on entire ecosystems. The objective of this dissertation is to understand how genetic variation in a riparian cottonwood species, Populus angustifolia, affects mass and energy exchange between the land and atmosphere across ~1700 km of latitude of the western United …

Microbial Community Dynamics Of A Microcystis Bloom, Helena Pound

Doctoral Dissertations

Harmful algal bloom events are notoriously associated with massive economic and environmental consequences, causing wildlife and human health risks. As these blooms increase in occurrence, duration, and severity around the world, it is essential to understand conditions leading to bloom formation and why they persist. Abiotic factors such as nutrients are commonly considered in bloom dynamics, but biotic interactions with co-occurring microbial species and viruses must also be taken into account. Harmful algal blooms dominated by the cyanobacterial genus Microcystis occur in bodies of water around the world and provide an ideal system in which to study top-down controls on …

The Effect Of Disturbance And Invasion On Fungal And Plant Communities Over An Elevational Gradient, Adam N. Trautwig

Doctoral Dissertations

High-elevation ecosystems are at risk of disruption from the future effects of climate change. Sub-alpine meadows are a source of unique plant populations, intraspecific variation of elevationally extreme populations, and vital sources of fresh water resources. We evaluated the whole fungal communities, arbuscular mycorrhizal fungal (AMF) communities, plant communities, and edaphic variables of sub-alpine meadows in undisturbed, disturbed, and disturbed with a non-native member of the Brassicaceae (Thlaspi arvense) plots. In conjunction with measuring the effects of disturbance on native communities we conducted potting experiments on a dominant grass of sub-alpine meadows (Festuca thurberi). We also …

Data Access, Distribution Models, And Stable Isotopes: Merging Approaches To Improve Bear Distribution Estimates And Bear Carnivory For Conservation, Nereyda Falconi

Doctoral Dissertations

My dissertation aims to contribute to the knowledge of Andean bears in Peru. The Andean bear (Tremarctos ornatus) is the sole bear species in south America. The lack of knowledge on different aspects of Andean bear ecology, biogeography, and abundance patterns hinders current conservation efforts for the species. I compiled Andean bear occurrence records in Peru with collaboration from many colleagues and created an open-access database at the GBIF data repository. Next, I modeled the distribution of Andean bear within Peru and compared estimates including and excluding unpublished records. I found that models combining published and unpublished records …

On Spatiotemporal Connectivity Dynamics: Perspectives From A Naturally Fragmented Metapopulation, Joseph Drake

Doctoral Dissertations

Connectivity has quickly become a central tenet of ecological research, frequently evoked for conservation research and management activities. However, the concept of connectivity has proliferated into many forms for many different perspectives. Generally said, population distributions, demography, landscape, and dispersal all contribute to connectivity in a meaningful way. While great progress has been made in increasing realism in connectivity, one component seemed to stand out as being underappreciated: the role of population dynamics in the application of landscape connectivity. I began to acquire an appreciation for how common modeling approaches make assumptions about these core components of connectivity. In Chapter …

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 …

Discovering Mechanisms Driving Adaptive Evolution In The Cross-Kingdom Fungal Pathogen Fusarium Oxysporum, Dilay Hazal Ayhan

Doctoral Dissertations

Fusarium oxysporum is a cross-kingdom pathogenic fungus that can cause vascular wilt disease in many economically important plants and local or disseminated infections in humans. Although it lacks a sexual stage in its life cycle, F. oxysporum can adapt to a wide range of hosts because of accessory chromosomes (ACs) which are enriched in host-specific genes and repeat content. This dissertation investigates the mechanisms that drive the adaptive evolution in the cross-kingdom pathogen F. oxysporum using comparative genomics and an experimental evolution approach. The first chapter compares phenotypes and genomes of a plant pathogenic isolate F. oxysporum f. sp. lycopersici …

Environmental Drivers Of Jaguar Distribution, Activity, And Abundance In Santa Rosa National Park, Costa Rica, Victor Montalvo

Doctoral Dissertations

Jaguars (Panthera onca) are a landscape species persisting in less than 54% of their historical distribution range; thus, the understanding of abiotic and biotic environmental factors affecting ecological interactions of this top predator in seasonal ecosystems such the dry forest is crucial for their conservation. In addition to factors affecting species ecology, some methodological constraints also could affect jaguar study outcomes leading to wrong decision-making. Data gathered from available jaguar peer-reviewed literature showed that there are large number of variables and techniques used to model jaguar distribution that did not contribute substantially to descriptions of jaguar distribution. Using …

The Hidden Life Of Tropical Roots: Functional Root Traits And Their Response To Climatic Disturbances, Daniela Yaffar

Doctoral Dissertations

Roots play a critical role in plant nutrition, and terrestrial carbon cycling. However, they are often understudied compared to their aboveground counterparts; especially in the tropics, where more carbon is cycled than in any other ecosystem. Some tropical forests, like in Puerto Rico, are more represented in scientific studies than others. However, this information is sparse, complicating the interpretation of root trait patterns. Trees in Puerto Rico have adapted mechanisms for withstanding hurricane disturbances, including in their roots. Additionally, as many tropical forests, some in Puerto Rico have low available phosphorus (P); thus, trees rely on root traits to enhance …

Applications Of Comparative Genomics And Data Science To Agricultural And Clinical Research, Katrina A. Schlum

Doctoral Dissertations

The advent of inexpensive, high-throughput whole genome sequencing (WGS) technologies has led to the generation of thousands of related genomes, even from a single study. Large-scale genome analysis has resulted in hypothesis-generating approaches in the fields of clinical, human and agriculture genomics. Additionally, population-level genomic sampling has resulted in a decrease in false positives in genotype-phenotype associations and an increase in understanding of the basis of disease, antibiotic and pesticide resistance. Deeper understanding of migration, genetic divergence and evolution has also been made possible due to WGS. This research applies comparative genomics, population genomics and data science approaches to whole …

The Effects Of High Temperatures On Mating Communication In Songbirds, Casey Marie Coomes

Doctoral Dissertations

Due to climate change, animals around the globe are experiencing the negative impacts of hot temperature extremes. Hot temperatures can affect animals is by inducing behavioral changes. Some of these behavioral changes include reductions in important, fitness-related behaviors such as foraging and mating. One aspect of mating behaviors that high temperatures can impact is communication. In many systems, mating communication consists of a male signaler transmitting a signal to a female receiver, who then uses the signal to assess the male’s quality as a potential mate. High temperatures can impact this process at the level of the signaler, the receiver, …

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 …

Social Context Influences On Behavior Of Carolina Chickadees, Brittany A. Coppinger

Doctoral Dissertations

This dissertation assesses fundamental social factors that drive variation in calling and other behaviors of experimental flocks of Carolina chickadees. Specifically, I tested how group member familiarity and group composition affected individual behavior. In addition, I performed a direct experimental test of the Social Complexity Hypothesis for Communicative Complexity, which states that groups that are more socially complex will communicate with greater signal complexity than groups that are less social complex. I consider complexity to be a combination of three factors: the number of parts in a system, the variation among the parts, and the variation in the way those …

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 …

Ecogeographical And Micromorphological Differentiation Between Selfing And Outcrossing Sister Species, Alannie-Grace Grant

Doctoral Dissertations

Since their emergence during the Cretaceous period, Angiosperms, or flowering plants, have achieved incredible success on land, colonizing an extensive range of environmental conditions and creating the structure of the Earth’s ecosystems. As they have adapted to these conditions, Angiosperms diverged in their niche breadth, morphological, physiological, biochemical, and phenological traits and evolved into the plant species known today. Some of the diversification within Angiosperm species is attributed to the adaptive evolution of floral traits that facilitate cross-fertilization by attracting and rewarding animal pollinators who transport their pollen or reductions in these traits to maximize self-fertilization.

In this dissertation, I …