Life Sciences Commons^™

Post-Fire Tree Mortality And Regeneration Patterns As Proxies Of Conifer Forest Resilience, Sebastian Upton Busby

Dissertations and Theses

Shifting wildfire patterns and climate conditions, magnified by anthropogenic climate change, are threatening the resilience of conifer forests in North America and more specifically, the western US. If native conifer species are functionally maladapted to novel fire patterns and post-fire climate conditions, large-scale shifts in conifer forest structure, composition, and extent may occur as warming intensifies. Forest resilience in the context of fire and climate can be understood and quantified by the survival of trees through fire events and success of trees to regenerate post-fire and maintain population levels. In this dissertation, I use field observations and remote sensing to …

Impacts Of Environmental And Anthropogenic Stressors On Amphibian Welfare, Diversity, And Distribution In The Upper Missouri River Basin, Kaitlyn Campbell

Dissertations and Theses

Climate change and anthropogenic stressors have contributed to rapid declines among various taxonomic groups; however, amphibian declines have been particularly intense and primarily stemmed from warming temperatures, habitat loss, exposure to contaminants, disease, and their subsequent interactions. Several climate mitigation strategies, like Bioenergy with Carbon Capture and Storage, have been proposed to alleviate the impact of rising temperatures; however, these proposals often fail to recognize and quantify the true impact on fauna, including changes in species distributions. To address this critical gap in knowledge, this research identified current amphibian distributions in the Upper Missouri River Basin and projected distribution changes …

Mitonuclear Mismatch Is Associated With Increased Male Frequency, Outcrossing, And Male Sperm Size In Experimentally-Evolved C. Elegans, Brent William Bever

Dissertations and Theses

We provide the first controlled study of how male frequencies and rates of outcrossing evolve in response to mitonuclear mismatch by allowing replicate lineages of C. elegans nematodes containing either mitochondrial or nuclear mutations of electron transport chain (ETC) genes to evolve under three sexual systems: facultatively outcrossing (wildtype), obligately selfing, and obligately outcrossing. In partial support of a tenet of the mitonuclear sex hypothesis, which predicts that outcrossing will be favored in cases of mitonuclear mismatch, we found evolution of increased male frequency in at least one replicate line of all four ETC mutant backgrounds tested--nuclear isp-1, mitochondrial …

Microbes On The Mountain: Plant-Microbe Associations And Interactions On Mount St. Helens, Emily Rose Wolfe

Dissertations and Theses

Plant-microbe associations and interactions provide critical context to studies in both community and ecosystem ecology, especially in systems that are relatively new and still undergoing early successional processes. Microbes can colonize the surfaces and interiors of all plant tissues, and these assemblages vary in composition both spatially and temporally, even within the same plant. Endophytes are bacteria or fungi that spend most of their lifecycles living within plant tissues asymptomatically--typically, "endophyte" refers specifically to aboveground tissues such as leaves and stems, and therefore may have direct influences on defenses against herbivory, pathogen or pest tolerance, and even afterlife effects on …

Exploring Linkages Between Landscape Patterns And Freshwater And Estuarine Bivalves In The Coast Range Of Oregon, Kaegan Michael Scully-Engelmeyer

Dissertations and Theses

Spatial configurations of landscape variables (biotic, abiotic, and socio-ecological) affect and are affected by ecological processes and species in watersheds. This dissertation explores relationships among landscape patterns, ecosystem processes and bivalve species dynamics in coastal watersheds in Oregon, USA. I approached this broad topic through two primary avenues of research: investigating cross-ecosystem threats from pesticide use in forestland management to downstream aquatic environments, and the landscape ecology of an at-risk freshwater mussel species.

Terrestrial land use activities present cross-ecosystem threats to riverine and marine species and processes. Specifically, pesticide runoff can disrupt hormonal, reproductive, and developmental processes in aquatic organisms, …

Spatial And Non-Spatial Patterns Of Genetic Diversity In Neotropical Bats, Andrea J. Calderon Brito

Dissertations and Theses

Macroecological studies that predict genetic diversity and its correlation with other biodiversity dimensions are essential to conservation in a rapidly changing environment. However, in bats (order Chiroptera), studies associating abiotic or ecological traits that could help to predict genetic diversity are scarce, even for singular species. In the Neotropics, the highest concentration of mammal and amphibian genetic diversity has been found in the Andes mountains and the Amazon Rainforest, yet it is an open question whether bat genetic diversity is also higher in these regions, or even if any abiotic factors are correlated with bat genetic diversity. Additionally, it is …