Digital Commons Network^™

Unraveling The Mystery Of Leaf Reddening In Seagrasses, Alyssa B. Novak

Doctoral Dissertations

Seagrass meadows around the world are declining due to natural and anthropogenic stressors, including global climate change. Recently, more attention has been given to identifying responses that offer resistance to stressors so that researchers can better manage seagrasses for resilience to environmental change. Leaf reddening, the expression of red coloration in leaves, is a well-documented response in terrestrial plants that has been shown to increase resilience to stress, but has been poorly understood in seagrasses. To increase our understanding of the prevalence, causes, and function of leaf in seagrasses, surveys were conducted in the world's six seagrass bioregions and a …

Study Of The Rate And Spectrum Of Spontaneous Mutations, Way Sung

Doctoral Dissertations

Mutations are the initial force responsible for all aspects of genetic variation, and are a central part to evolution in all organisms. Yet despite its importance, the previously high cost that is associated with surveying mutations at a genome-wide scale has limited the understanding of the mutation process in eukaryotes. However, recent high-throughput sequencing technology has greatly reduced the cost of surveying mutations. By applying high-throughput sequencing to mutation accumulation experiments, we have begun to characterize the genome-wide mutation spectrum of eukaryotes.

Across all eukaryotes, we observe a biased rate of G/C-> A/T mutations that exceeds the number of A/T- …

Satellite-Derived Fluorescence Quantum Yields As Indicators Of Phytoplankton Photophysiology, Deborah Goodwin

Doctoral Dissertations

Understanding and quantifying phytoplankton physiological variability is essential for analyses of biogeochemical cycling, climate change and ecosystem processes. Satellite measurements of chlorophyll indicate phytoplankton biomass but hold minimal direct information about the organisms' photosynthetic capabilities: however, remote sensing-derived fluorescence quantum yields have the potential for monitoring phytoplankton photophysiological states on a global scale. Recent research has demonstrated the effects of both nutrient stress and photoacclimation on fluorescence yield. Here, a novel satellite product comprising seven years of fluorescence quantum yields, derived from MODIS/Aqua normalized fluorescence line heights and corrected for pigment packaging effects, is evaluated and explored. Fluorescence yields are …

Character Displacement In Burkholderia Biofilm Communities And The Effect Of Adaptive History On The Evolution Of Niche Breadth, Crystal Nicole Ellis

Doctoral Dissertations

Ecologists agree that biodiversity is essential for maintaining highly productive and stable ecosystems, yet the mechanisms that generate and preserve diversity are unknown in many habitats. Competition for shared resources may cause selection to favor niche specialization, which reduces competition and reinforces diversity. If the environment is significantly altered, the ecological history of the remaining colonizer may influence fitness and capacity for diversification in new environments. In many cases, specialists have limited adaptive potential due to trade-offs generated by niche-specific adaptation; however, generalists may be adaptable in many habitats, which would make them good pioneer species for colonization. We investigated …

Assessing Social-Ecological Resilience And Adaptive Capacity In The Face Of Climate Change: An Examination Of Three Communities In The Crown Of The Continent Ecosystem, Bradley B. Johnson

Doctoral Dissertations

This research examines the social-ecological resilience and adaptive capacity of the Crown of the Continent Ecosystem through a suite of three case study communities and the impacts of climate change on the ecosystem's hydrologic regime. The Crown of the Continent Ecosystem spans the U.S.-Canadian border; case study communities composed of Kalispell and Choteau, Montana and Fernie, British Columbia fall on both sides of the border.

Primary data was gathered through a "bottom-up" qualitative approach utilizing an online survey followed by a semi-structured interview process with stakeholders in natural resource dependant industries and government at the local, state, and federal levels …

Detection Of Mortality In Tropical Forests Using Remote Sensing: From Treefall Gaps To Large Disturbances, Fernando Del Bon Espirito-Santo

Doctoral Dissertations

The frequency, severity, and intensity of natural disturbances in tropical forests continually re-shape forest structure. At small scale, branch or tree-falls gaps and subsequent recovery are important mechanisms for carbon cycling. At landscape scale, large disturbances (blow-downs) may also play a role on the structure and composition of tropical forests. Quantitative studies of natural disturbances across the occurrence spectrum (branch fall-gaps to blow-downs) are rare for the Amazon. Remote sensing coupled with intense field work data collection provides the means to analyze the dynamic of tropical forests at multiple scales. In this dissertation three aspects of natural disturbances were examined: …

Seasonal, Biogeochemical, And Microbial Response Of Soils To Simultaneous Warming And Nitrogen Additions, Alexandra R. Contosta

Doctoral Dissertations

Climate warming and nitrogen deposition are global environmental threats that could alter soil microbial communities and the biogeochemical processes they perform. Few studies have examined interactive effects of elevated temperatures and nitrogen inputs. Many studies have also not considered the role that season plays in mediating the response of soils to warming and nitrogen. Finally, most research has not linked changes in the soil microbial community with ecosystem-scale dynamics. One objective of this dissertation was to examine season-specific microbial and biogeochemical responses to simultaneous warming and nitrogen additions. Another aim was to investigate whether warming and nitrogen can restructure microbial …

Existing Regulatory Circuitries Govern Backbone And Acquired Host Association Factors In The Human Pathogen Vibrio Parahaemolyticus, Jennifer C. Mahoney

Doctoral Dissertations

Vibrio parahaemolyticus is a poorly characterized human gastrointestinal pathogen whose virulence mechanisms are not well understood. Though closely related to Vibrio cholerae, V. parahaemolyticus infections are inflammatory and utilize virulence traits that are unique from the Cholera toxins yet remain poorly characterized. Vibrio spp. in general share an extensive core genome dedicated to environmental survival and unique, often horizontally acquired, gene content that is reserved for species specific lifestyles. This diversity has resulted in a genus of highly specialized bacteria partaking in dramatically different lifestyles ranging from symbiosis to pathogenesis. We propose that a comparative genomic and transcriptomic analysis of …