Biology Commons^™

Novel Indices To Quantify Freeze Tolerance In Amphibians, Jolene R. Rearick

Biology ETDs

We propose Freeze Endurance (F_end) as a new measure of the ability of amphibians to tolerate internal freezing, allowing integration of time and temperature to describe each freeze event. Use of freeze endurance as a descriptor allows direct comparison between individuals, populations, and species, and may be scaled by body size, or other characteristics, to determine if abilities to survive freezing are significantly different between groups. Thermal limit examinations have long suffered from lack of comparability between publications due to differing endpoints, measurements, equipment, and organism availability, despite the value of information yielded by such studies to understanding …

Novel Approaches To Exploring Silk Use Evolution In Spiders, Rachael Elaina Alfaro

Biology ETDs

Spider silk is enigmatic, and web structure, design, and adult morphology of the spinning apparatus of spiders once informed how systematists approached the spider phylogeny. The orb-web and adaptation of viscous silk was considered a key innovation leading to rapid diversification of spiders. However, the advent of molecular techniques including recent phylogenomics studies, overturned this major paradigm in spider evolution. Clades once considered monophyletic are no more. The orb-web is not a pinnacle of evolution, and the former sister group, using cribellate silk (loops of fibrils combed from a specialized silk plate on the abdomen), is now sister to the …

Where The Wild Things Are: Investigating Body Size As A Mechanism For Persistence, Meghan Anne Balk

Biology ETDs

Body size is a trait under selection. Genetic drift, climate, diet quality, and biotic interactions all select upon body size at the population, species, and community levels. These factors can be important in the context of rapidly changing climate. One of the ways an animal can persist in its environment is through morphological adaptation in situ. Here, I investigate four questions relating to the evolution of body size: (1) what is the limit in body size change in response to climatic change; (2) how does body size influence the thermal tolerances of animals; (3) how does body size evolve …

Mitigating The Impacts Of Human Land-Use Change On Biodiversity: With A Focus On Large Migratory Herbivores, Kina Rebekah Murphy

Biology ETDs

Land-use change, commercial over-harvesting of species, and climate change are recognized as the main drivers of biodiversity loss. As a result, it is estimated that 30% of the planet’s biodiversity may go extinct by 2050. This dissertation focuses on how to mitigate the impacts of land-use change on biodiversity. I focus on large migratory herbivores because they are among the most heavily impacted by global change due to their large home range requirements. Habitat fragmentation, illegal hunting, and human-wildlife conflicts are among the biggest threats to large herbivores and result from land-use change. For this reason, my first chapter focuses …

Biogeography, Interspecific Introgression, And The Evolution Of Hemoglobin Genes In The High Andes: The Evolutionary History Of The South American Siskins (Spinus), Elizabeth Jane Beckman

Biology ETDs

Landscape features, interspecific introgression, and adaptation work in concert to shape the evolutionary history of a clade. Understanding the independent and cumulative consequences of these evolutionary processes on diversification is critical to revealing the origins of extant biodiversity. Studying these processes within rapid radiations, a significant contributor to global biodiversity, can provide powerful insight into the process of diversification. To assess how diversification is shaped by these evolutionary forces, I examined the biogeographic history, patterns of interspecific introgression and adaptation to high elevation in a recent, rapid radiation of finches, the South American siskins (Fringillidae: Spinus). I found that …

Shifts In The Relative Importance Of Competition And Mutualism For Communities And Ecosystems, Lukas Patrick Bell-Dereske

Biology ETDs

Plant species interact with at least one, likely many, microbial mutualist throughout their life cycles. These microbial mutualists can have strong effects on plant communities and ecosystem processes. Fungal endophytes within the genus Epichloë associate with ~20%–30% of grass species and have been shown to have strong effects on plant communities. Here I described the effect of Epichloë amarillans associated with the dominant grass species, Ammophila breviligulata, on nutrient cycling, below-ground microbial community, and compare the strength of its effects on plant communities to plant-plant competition.

In chapters one and two, I examine the effects of Epichloë on litter …

The Molecular Systematics And Phylogeography Of The Widespread North American Meadow Vole (Microtus Pennsylvanicus), Donavan J. Jackson

Biology ETDs

The climatic and environmental fluctuations of the Quaternary played an integral role in geographic distribution and genetic structure within many organisms today. Understanding how these historical biogeographic events may have partitioned genetic variation throughout the landscape is critical to forecasting the implications of modern climate change and how animals will respond to projected climate shifts. Through geographic and taxonomically comprehensive sampling, we used multi-locus and species delimitation analyses along with niche modeling methods to investigate the evolutionary and biogeographic history of the meadow vole, Microtus pennsylvanicus. The findings of this study highlight the vulnerability and importance that special consideration …

Plant-Biocrust Interactions Mediated By The Fungal Loop, Eva Dettweiler-Robinson

Biology ETDs

Plant-microbial interactions influence biogeochemical cycles. Plants and biological soil crusts are primary producers in drylands. Biocrusts include cyanobacteria, lichens, mosses, algae, fungi, bacteria, and archaea on the soil surface, some of which fix atmospheric nitrogen. I investigated controls on biocrust carbon fluxes and their contribution to ecosystem fluxes, the incorporation of plant-derived carbon into biocrusts, and the role of soil fungi in promoting performance of plants and biocrusts. Biocrusts responded to temperature and moisture differently by biome. Biocrusts in grasslands/shrublands contributed >25% of total summertime ecosystem respiration, but biocrusts in savannas/woodlands contributed < 1%. Biocrusts contributed < 2% to GPP in any biome. To augment their native photosynthesis, biocrusts may include 16% plant-derived carbon. Fungal connections improved plant and biocrust performance and reduced differences in the CN ratio between organisms compared to when connections were impeded. Investigation of interactions among biocrusts, plants, and fungi has improved understanding of resource cycling in drylands.

Montane Valley Grassland Plant Communities Are Highly Resistant To Wildfire, Martina M. Suazo

Biology ETDs

Understanding the ecological role of fire in fire-adapted plant communities is of great importance for restoration and preservation; however, limited research has been conducted on the response of upper elevation, C₃ grassland plant communities to wildfire. This study investigates the effects of the Las Conchas wildfire of 2011 on plant community structure and function in the montane valley grasslands of the Valles Caldera National Preserve, Jemez Mountains, New Mexico, USA. Long term monitoring of nine burned and seven unburned grassland sites was used to measure vegetation composition and dynamics both spatially and temporally relative to fire. Results show that …

Patterns In Richness And Community Structure: From Bacteria To Apex Predators, Ara S. Winter

Biology ETDs

Patterns of community structure and richness provide context for studies from microbial ecology, global macroecology, languages, to Bayesian statistics. Diversity patterns for animals on land and their predictor variables are well studied. However, diversity patterns for bacterial communities and marine macroorganisms are not well studied or understood. Here I examine diversity patterns in caves, on the external surface of Chiroptera (bats), and in marine ecosystems. At the local to regional scale we investigate factors that drive bacterial community patterns in richness and composition in lava cave microbial mats and microbes on bats. Lastly, out of the cave and into the …

Coevolving Histories Inside And Out: Phylogenetics, Comparative Parasitology, And Host Affinities Of Chipmunk Sucking Lice And Pinworms, Kayce C. Bell

Biology ETDs

Diversification of parasite species, in light of their host association, is an area ripe for testing hypotheses of evolution when one species requires another for survival. The 23 species of western North American chipmunks (genus Tamias) host two species of ectoparasitic sucking lice (Anoplura) and two species of endoparasitic pinworms (Nematoda). I used a phylogenetic approach to investigate the evolutionary histories of the parasites in light of the hosts and the landscape. In comparing the parasites, I found that the two pinworm species have similar diversification patterns, linked to hosts, but those processes occurred on different time scales. As another …

Energetics Across Ecological Scales, John M. Grady

Biology ETDs

Energy is a common currency of ecological interactions. In this dissertation, I consider ecological energetics at different temporal, spatial and organizational scales. In my first chapter, I examine the energetics and thermoregulation of an enigmatic taxon: dinosaurs. From fossil evidence and assessment of living vertebrates I conclude that many non-avian dinosaurs were likely thermally intermediate, or 'mesothermic'. In my second chapter I detail the empirical evidence gathered to buttress my claim of dinosaur mesothermy. In my third chapter, I show how ecosystem rates of carbon flux, gross primary production and total biomass can be linked to individual body size. In …

Altitudinal Gradients Do Not Predict Plant-Symbiont Responses To Experimental Warming, Melanie R. Kazenel

Biology ETDs

Fungal symbionts, ubiquitous inhabitants of above- and belowground plant tissues, can play important roles in increasing plant tolerance to abiotic and biotic stress. Disruption of plant-fungal interactions may therefore have important consequences for plant responses to climate change. Both altitudinal gradients and warming experiments can be useful tools for understanding responses of symbioses to climate shifts, but the degree to which altitudinal patterns will predict species responses to warming has received little attention for plant-symbiont interactions. This study combined surveys along replicated altitudinal gradients with a long-term warming experiment at the Rocky Mountain Biological Laboratory (RMBL) in Colorado, USA to …

Phylogenetics And Diversification Of Whirligig Beetles (Coleoptera, Gyrinidae), Grey Thomas Gustafson

Biology ETDs

Whirligig beetles are a family of aquatic beetles with an estimated 1,000 species distributed globally. Phylogenetic analysis incorporating molecular data has only recently been conducted on the family and many genera have never received modern taxonomic revision. The first chapter of the dissertation provides a taxonomic revision of the Southeast Asian whirligig beetle genus Porrorhynchus, finding the genus to contain 5 species, and no support for the numerous proposed subspecies. For the second chapter a phylogenetic analysis utilizing the most novel phylogenetic reconstructions methods incorporating the new Fossilized Birth-Death macroevolutionary model implemented in the program MrBayes 3.2.6 was conducted on …

Experimental Drought And Soil Depth Interactively Influence Fungal Community Composition In Piñon-Juniper Woodland, Eric Olivas

Biology ETDs

Drought can flip ecosystems between states and in the process alter key systems such as plant biomass and carbon balance. Many drought-related studies have focused on plant responses or charismatic megafauna. Less work has addressed drought in the context of aboveground-belowground feedbacks. Impacts of drought are increasing, particularly in arid environments such as the southwestern United States. Major tree species of these regions, such as piñon pine, are adapted to a wetter and more predictable climate than the projected future climate. The effects of drought on piñon and its ectomycorrhizae have been studied observationally and in laboratories. Soil depth has …

Mammals Of The Greater Gila Region, Amanda K. Jones

Biology ETDs

The Greater Gila Region is an important area for study of mammals due to its unique physiographic history, leading to high elevational relief and many associated habitats. Due to the variety of habitats, the Gila is home to a very diverse assemblage of mammal fauna: 100 native species, 95 of which are extant in the region. This paper documents these species' current and historic distributions, taxonomy, habitat affinities, current phylogeographic studies, reproductive timing, and any other pertinent information. In addition, novel phylogeographic studies for four selected species were performed to fill in gaps in previous studies where Gila sampling was …

A Multidimensional Investigation Of The Niche: Geographic Distributions, Body Size, And Interspecific Interactions Of Late Quaternary North American Canidae, Melissa Irene Pardi

Biology ETDs

A pressing conservation challenge is understanding how organisms will be impacted by climate change. From the paleontological record, we know organisms have options when facing change: they can do nothing, move, or adapt. These responses shape an organism's niche (a foundational concept in biology) that is abiotically constrained, but modified by biotic interactions. The greatest disturbances in recent North American geologic history is the human mediated extinction of megafauna ~11,700 years B.P. and climate change following the last glacial period. We used the fossil record to address ecological questions concerning conservationists; our focus was on Canidae and humans. Species distribution …

Retrospective Food Web Analysis Of Gila River Fishes Reveals Hydrologic Parameters Influence Non-Native Species Effects, Rosalee Anne Reese

Biology ETDs

The relatively pristine upper Gila River in New Mexico is a stronghold for endemic native fishes despite the presence of non-native fishes. In other, more severely human-impacted tributaries in the Colorado River basin, non-native fishes are a major factor in native species decline and extirpation. I tested whether presumed negative effects of non-natives on natives are compounded during drought using an approach based on Stable Isotope Analysis (SIA) and comparisons of resource use overlap during different flow conditions. Fish specimens were selected from natural history collections to represent a time series that encompassed wet and dry years, as well as …

Paratransgenic Control Of Pierce's Disease, Arinder K. Arora

Biology ETDs

Pierce's Disease (PD) is a deadly grapevine disease, which is caused by a Gram negative bacterium, Xylella fastidiosa and transmitted by leafhoppers commonly known as sharpshooters, including the glassy-winged sharpshooter (GWSS, Homalodisca vitripennis). We developed paratransgenic control of PD using a commensal bacterium Pantoea agglomerans E325. The GWSSs acquired enhanced green fluorescent (EGFP)-expressing P. agglomerans from an artificial feeding system and the bacteria persisted within the insect foregut for two weeks. P. agglomerans was selected as the paratransgenic control agent based on its persistence within the sharpshooter foregut, a niche also inhabited by X. fastidiosa. P. agglomerans lines secreting two …

Transcriptional Regulation Of Muscle Development In Drosophila Melanogaster, Tonya M. Brunetti

Biology ETDs

The transcriptional regulation of muscle development involves several complex processes that must work together in order to form functional, syncytial muscle cells. However, when transcription is mis-regulated, muscle development is often times negatively affected and can lead to muscle diseases such as muscular dystrophy and cardiac myopathies. In order to gain more insight into how transcription is regulated, I use Drosophila melanogaster as a model for understanding muscle development. In chapter one, I use a traditional genetic screen to phenotypically and molecularly identify two Hox co-factors, extradenticle and homothorax, that have the ability to change muscle identity. Additionally, in chapter …

Flight Muscle Progenitor Populations In Drosophila Melanogaster, Elizabeth Carvosso Clarke

Biology ETDs

We use the Drosophila system to define how genes control muscle development and function. Many of the genes in the fruit fly, Drosophila melanogaster, are conserved with higher animals, and so our results can be important in understanding mechanisms of vertebrate muscle development and disease. Study of the flight muscle progenitor populations in Drosophila gives clearer understanding of the genetic regulatory networks that lead to the development of flight muscle. The direct flight muscles (DFMs) and indirect flight muscles (IFMs) arise from the myoblast population of the notal region of the Drosophila wing imaginal disc. Within the myoblast population, there …

A Life History Of The Roundnose Minnow, Dionda Episcopa, In The Middle Pecos River Valley, New Mexico, Michael A. Farrington

Biology ETDs

Life history aspects of Roundnose Minnows, Dionda episcopa, were examined for specimens collected between 2011 and 2013 in El Rito Creek, near Santa Rosa New Mexico. A recent study examining DNA suggested that, instead of supporting a widespread population of the Roundnose Minnow, New Mexico is actually home to two evolutionarily distinct Roundnose Minnow populations. This focus of this study is on the life history attributes of what may become a newly described species of Dionda. Modal class progression analysis (Bhattacharya method) documented four distinct age classes of Roundnose Minnows within El Rito Creek. Sex ratios deviated from the expected …

Gene Duplications During Experimental Evolution Of Caenorhabditis Elegans: Duplication Rates And Evolutionary Responses, James Charles Farslow

Biology ETDs

Copy-number variants (CNVs) are a ubiquitous form of genetic variation. How often this form of variation arises and its adaptive significance are active areas of contemporary research. This work presents evidence regarding both of these subjects. First, it demonstrates that gene duplications occur at a frequency two orders of magnitude greater than point mutations. Specifically, the gene duplication rate is estimated to be 1.2 x 10-7/gene/generation, compared to a point mutation rate on the order of ~10-9/site/ generation. Second, it was found that populations in a low state of fitness due to mutation accumulation could recover some or all of …

The Impact Of Temperature, Ph And Environmental Heterogeneity On Prokaryotic Diversity In Yellowstone National Park Thermal Springs, Xiaoben Jiang

Biology ETDs

Yellowstone National Park (YNP) is one of the largest and most diverse hydrothermal areas on Earth. Extensive culture-independent studies in YNP thermal springs have shown dramatic taxonomic and metabolic diversity in microbial communities. We conducted a survey of bacterial communities along temperature gradients in three alkaline springs with similar geochemistries at the local scale. With these data, we investigated the influence of environmental variables on bacterial community diversity and assemblages along a broad temperature range using high throughput 454 pyrosequencing. Previous studies have suggested that pH is the driver of microbial diversity in thermal springs among geographical regions or at …

Quantifying Temperature Sensitivity Of Soil Respiration Across A Range Of Semi-Arid Biomes, Michelle Nuanez

Biology ETDs

Soils in semi-arid regions store approximately 10% of earths soil organic carbon, the substrate which microbes oxidize, resulting in the largest source of carbon to the atmosphere from terrestrial ecosystems. Semi-arid regions are expected to experience increased temperatures and altered precipitation regimes over the next 100 years, altering soil temperature and water, the two predominant drivers in soil respiration processes. In this study we quantify the temperature sensitivity of soil respiration in five semi-arid biomes ranging from desert grassland to ponderosa pine forest along an elevational/climate gradient in central New Mexico. We measured statistically similar temperature sensitivities in 4 of …

Effects Of Stream Edges On Algal Biomass In The Middle Rio Grande, Steven Daniel Scholle

Biology ETDs

In river systems, there are many factors that impede or facilitate algal standing stock and therefore impact primary production in these environments. I am particularly interested in the influence of edges in riverine systems and how these geomorphic features affect the available surface area for algal production. This study investigates the middle Rio Grande system near Albuquerque, New Mexico, USA. The middle Rio Grande is a turbid, partially braided lotic ecosystem. Although edge characteristics can vary widely, especially between errosional and depositional banks, I hypothesize that edges become important zones of primary production, due in part to decreased water depth, …

Disturbance Events In Arid Ecosystems: Comparisons Of Enzyme Activity Profiles Across Multiple Soil Microbial Communities, Daniel Douglas Warnock

Biology ETDs

Arid ecosystems are home to approximately 35% of earth's human population, and approximately 40% of earth's terrestrial carbon. These systems are especially prone to releasing the stored carbon when under global climate change (GCC) related pressures. My goal for these studies was to expand on our already growing knowledge base of how the soil microbial communities in disturbed arid ecosystems undergo shifts in functional patterns, as they respond to a rapidly changing environment. In chapter two, I examined the overall functional activity levels and functional behaviors exhibited by both pinon and juniper supported RAM communities in the context of widespread, …

Comparative Study Of Genomic Features Of Evolutionarily Young Gene Duplicates, Lijing Bu

Biology ETDs

Gene duplication is considered a major contributor to genome evolution and functional diversity. Differences in genomic features (such as structural resemblance, transcriptional orientation, and genomic location) between members of a gene duplicate pair may indicate the possible duplication mechanisms, as well as the evolutionary fates the paralogs may experience. In addition to these genomic features, molecular genetic features, such as differences in codon usage and expression levels may provide further insight into functional changes between paralogs. In this dissertation, multiple genomic analyses were conducted in order to evaluate the differences in genomic and genetic properties between duplicate copies in order …

Macroecology And Sociobiology Of Humans And Other Mammals, Joseph Robert Burger

Biology ETDs

Despite being the most studied species on the planet, ecologists typically do not study humans the same way we study other organisms. My Ph.D. thesis contributes to scientific development in two ways: i) synthesizing our understand of the inter and intraspecific variation in social behavior in an understudied rodent lineage, the caviomorphs, providing a comparative context to understand social evolution in general, and 2) developing a macroecological approach to understand the metabolic trajectory of the human species. Through comparative analysis, chapter 2 synthesizes the available information on the diversity of sociality in the caviomorph rodents, both within and across species. …

Foliar Respiration And Carbon Dynamics Of Mature Piñon And Juniper Trees In Response To Experimental Drought And Heat, Adam D. Collins

Biology ETDs

Plant respiration (R) is generally well-coupled with temperature and in the absence of thermal acclimation, respiration is expected to increase as climate change brings higher temperatures. Increased drought is also predicted for future climate, which could drive respiration higher if the carbon (C) cost to maintain tissues (Rm) or grow increases, or lower if substrate or other factors become limiting. We examined the effects of temperature and drought on R as well as photosynthesis, growth, and carbohydrate storage of mature individuals of two co-dominant tree species. Three mature, in-situ piñon (Pinus edulis) and juniper (Juniperus monosperma) trees were assigned to …