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Articles 31 - 60 of 639
Full-Text Articles in Biology
Metagenomic Analysis Of Antarctic Microbial Communities, David Michael Robinson
Metagenomic Analysis Of Antarctic Microbial Communities, David Michael Robinson
Biology ETDs
The research presented in this dissertation focuses on microbial roles in biogeochemical cycling in Antarctic aquatic environments. The major objective of my research was to examine the impact of biotic and abiotic pressures on nutrient cycling in microbially dominated systems. I used three perennially ice covered lakes in the McMurdo Dry Valleys (MDVs) along with subglacial lakes Whillans and Mercer as natural case studies. The MDVs are located in Victoria Land, East Antarctica and have been studied since 1993 as part of the McMurdo Long Term Ecological Research Project. Viruses in the MDVs were shown to be seasonally abundant and …
Increasing Bacterial Tolerance And Metabolism Of The Biofuel, N-Butanol Using Community-Level Evolution And Functional Genomics, Kayley T. You Mak
Increasing Bacterial Tolerance And Metabolism Of The Biofuel, N-Butanol Using Community-Level Evolution And Functional Genomics, Kayley T. You Mak
Biology ETDs
Bioremediation capability should be developed along with biofuel technology to mitigate the potential damage of future spills. Biobutanol is being developed since n-butanol is more energy dense and less volatile than ethanol. A bottleneck for industrial production of biobutanol is its toxicity; most microbes cannot survive ~1.5% v/v. Thus, microbial bioremediation of n-butanol would need microbes that can both tolerate and metabolize butanol. We used ecological and evolutionary biology approaches to find bacteria that could tolerate and metabolize butanol. Ecological community-level assays followed by 16S amplicon sequencing were completed to identify butanol-tolerant artificial bacterial communities. Secondly, we looked for bacteria …
Variability In Large Mammal Activity Patterns When Visiting Water In New Mexico, Juan E. Camacho
Variability In Large Mammal Activity Patterns When Visiting Water In New Mexico, Juan E. Camacho
Biology ETDs
Studying activity patterns of animals can provide vital information about how different species react to environmental changes, yet camera trap studies typically neglect the temporal aspect of the data. Using a 10-year camera trap dataset on Sevilleta National Wildlife Refuge, NM, we explored daily activity patterns when visiting water of five large mammal species. The species of study were mule deer, pronghorn, elk, oryx, and coyote. All species showed significant variability in activity patterns from site to site across the refuge. Within a site, differences in activity across years and seasons were less pronounced. Mule deer and coyote showed very …
Unraveling The Paradox Of The 'Great Speciators': Evolutionary Dynamics Of A Geographic Radiation Of Island Kingfishers (Todiramphus), Jenna Merle Mccullough
Unraveling The Paradox Of The 'Great Speciators': Evolutionary Dynamics Of A Geographic Radiation Of Island Kingfishers (Todiramphus), Jenna Merle Mccullough
Biology ETDs
The paradox of the ‘Great Speciators’ describes a biogeographic pattern in which geographically widespread lineages have strong overwater dispersal capabilities, yet exhibit genetic and phenotypic divergence between islands, suggesting limited dispersal and cessation of gene flow. In my dissertation, I leveraged whole genomes and two comprehensive trait datasets of dispersal ability and plumage coloration of all described diversity within Todiramphus kingfishers, a rapid radiation of largely island endemic ‘Great Speciators.’ Chapter 1 reveals that whole genome datasets do not outright solve the evolutionary relationships of this clade and that widespread incomplete lineage sorting (ILS) and gene flow are sources of …
New Insights Into T Lymphocyte-Mediated Immunity To Toxoplasma Gondii, Claire Marie Doherty
New Insights Into T Lymphocyte-Mediated Immunity To Toxoplasma Gondii, Claire Marie Doherty
Biology ETDs
With nearly a third of the global population infected with the protozoan, Toxoplasma gondii, this parasite sits at a unique, immune-mediated interface of health and disease. In healthy individuals, Toxoplasma results in a chronic yet asymptomatic infection of the central nervous system. This quiescent infection is the result of parasite exploitation of host immune barriers, yet Toxoplasma can quickly become an opportunistic pathogen when immunity is disrupted by illness or immunosuppressive therapies. During the HIV-AIDS pandemic, it was observed that once latent Toxoplasma infections became the cause of severe, even fatal, disease in the absence of an intact T …
Crossing The Ocean: The Importance Of Gene Flow In Island Evolution, Ethan F. Gyllenhaal
Crossing The Ocean: The Importance Of Gene Flow In Island Evolution, Ethan F. Gyllenhaal
Biology ETDs
Islands have long been a critical arena for the development of ecological and evolutionary theory, particular due to persistent open-water gaps between them. In this dissertation I demonstrates how these caps are permeable, which can be leveraged to understand evolution on islands and more broadly. The first chapter develops this connection between ongoing, overwater gene flow and island biogeographic theory, and tests it on an archipelago species. The second take a three-pronged approach in demonstrating how over-water gene flow can bias phylogenetic inference, and how many phylogeographic metrics in islands are likely shaped by long-term gene flow. The final two …
The Descent Of Anolis: Assemblages, Convergence, And Ecomorphological Evolution, Christopher G. Anderson
The Descent Of Anolis: Assemblages, Convergence, And Ecomorphological Evolution, Christopher G. Anderson
Biology ETDs
The evolutionary outcomes we observe in modern organisms, particularly associations between phenotypes and environments, have been and remain an invaluable tool in interpreting the biological phenomena that shape our world. In the following chapters, I leverage a comprehensive phylogenetic and morphological dataset for 351 species comprising a diverse group of arboreal lizards, the Anolis clade, to explore how communities and morphologies evolve. First, I characterized patterns among coexisting lineages of Anolis to reveal a general pattern of phylogenetic relatedness among lineages comprising assemblages and identify differences attributable to a biogeographic variable. Then I examined the morphological consequences associated with the …
Quantifying The Influences Of Abiotic And Biotic Factors On Post-Fire Vegetation In The Southwestern Us, Joseph Lafayette Crockett
Quantifying The Influences Of Abiotic And Biotic Factors On Post-Fire Vegetation In The Southwestern Us, Joseph Lafayette Crockett
Biology ETDs
The ongoing warming associated with climate change is increasing the flammability of southwestern US dry forests. As larger fractions of the landscape are impacted by high-severity fire, the potential exists for forests to convert to non-forest. Given that the forested area in the southwestern US is an important contributor of ecosystem services, quantifying limitations to vegetation establishment is critical to informing post-fire recovery efforts and understanding how ongoing climate change will limit seedling establishment in the future. To that end, this dissertation focuses on post-fire vegetation recovery of southwestern forests. First, I report on the influence of precipitation and topography …
Phenological Activities Of Desert Bees Track Rainfall More Than Temperature And Predict Temporal Abundance Trends Over 16 Years, Jade Elijah Mclaughlin
Phenological Activities Of Desert Bees Track Rainfall More Than Temperature And Predict Temporal Abundance Trends Over 16 Years, Jade Elijah Mclaughlin
Biology ETDs
Phenology, the timing of recurrent biological events, is a key mechanism by which species adapt or acclimatize to variable environmental conditions, including those influenced by climate change. Measurable traits, including the onset and end of activity, peak activity, and duration, characterize the phenology of life events, and could be significant predictors of trends in population abundance or stability in a changing climate. Bees provide critical pollination services, and understanding the covariates of bee phenological traits can refine predictions on the vulnerabilities of bees and their services to climate change. We paired 16 years of monthly bee survey data (2002-2019) with …
Mimicking Biofilms: Photosynthetic Assessments Of C. Reinhardtii In 3 Physical Forms, John Michael Roesgen
Mimicking Biofilms: Photosynthetic Assessments Of C. Reinhardtii In 3 Physical Forms, John Michael Roesgen
Biology ETDs
Oxygenic photosynthesis supports the majority of life on Earth through the capture of energy from sunlight and the assimilation of CO2 into basic building blocks of cells. Microalgae are fast growing and account for about half of global photosynthesis. In addition, they can be cultivated and their metabolism can be redirected to generate additional useful products ranging from biofuels to pharmaceuticals. However, the efficiency of metabolite production is severely impacted by the slow diffusion of CO2 through water and the high energetic costs of harvesting microalgae from liquid cultures. Microalgae grow in open water, but they also form …
An Investigation Of Freshwater Turtle Ecology Using Stable Isotopes, Jonathan Duran
An Investigation Of Freshwater Turtle Ecology Using Stable Isotopes, Jonathan Duran
Biology ETDs
In 2022 I investigated niche partitioning among native and invasive freshwater turtles across three sites in the Middle Rio Grande using bulk stable isotope analysis. I found high degrees of niche partitioning at sites in which Red-eared sliders (Trachemys scripta) have yet to establish. However, at sites in which red-eared sliders are now the most abundant species they overlapped greatly in isotopic niche with all native turtles, in particular the painted turtle (Chrysemys picta). Using these same techniques, I then examined the trophic interactions between red-eared sliders and their acanthocephalan parasites. My results suggest that acanthocephalans …
Diversification By Dispersal Out Of The Andes Revealed By A Newly Discovered Hummingbird Clade, The ‘True Brilliants’, Marialejandra Castro-Farías
Diversification By Dispersal Out Of The Andes Revealed By A Newly Discovered Hummingbird Clade, The ‘True Brilliants’, Marialejandra Castro-Farías
Biology ETDs
We identified a novel clade with striking biogeographic implications. Unsampled genera, Hylonympha and Sternoclyta, were found to be close to the genus Heliodoxa within the Brilliants. Heliodoxa tend to occur in lower montane habitats, such as the tropical, upper tropical, and subtropical elevational zones of the Andes and the Neotropics. Analysis of geographic and elevational zones showed that genus Heliodoxa and related genera diversified by out-of-Andes dispersal to mountain ranges of Central America, coastal Venezuela, the Pantepui, and southeastern Brazil, since the mid-Miocene. Within the Brilliants, reductions in elevation preceded these geographic expansions. Secondary colonization of the lowlands from …
Post-Fire Plant Community Response In Subalpine Mixed Conifer Forest, Sasha Escamilla
Post-Fire Plant Community Response In Subalpine Mixed Conifer Forest, Sasha Escamilla
Biology ETDs
Increased wildfire activity may lead to significant shifts in vegetation dynamics in high elevation mixed conifer forests. These changes raise concerns about the resilience of forests following wildfire, prompting the need for a deeper understanding of post-fire plant community response. We analyzed up to 11 years of post-fire vegetation data from Valles Caldera National Preserve in northern New Mexico to determine how burned vegetation sites were recovering following high severity wildfire, and whether or not plant communities were transitioning to montane grassland. We found burned understory herbaceous communities were not transitioning into distinctive montane grasslands and were instead recovering to …
Evidence Of Competitive Release Following Overstory Mortality In A Semi-Arid Piñon-Juniper Woodland, Corrie D. Gonzalez
Evidence Of Competitive Release Following Overstory Mortality In A Semi-Arid Piñon-Juniper Woodland, Corrie D. Gonzalez
Biology ETDs
Extreme temperatures and severe drought events have led to widespread tree mortality worldwide. In semi-arid regions of the Southwest United States, these events pose a significant threat to piñon-juniper (PJ) woodlands. We studied the effects of piñon and juniper mortality on the growth and physiology of existing saplings in PJ woodlands by analyzing water status, photosynthetic activity, and tissue chemistry to gain insights into these impacts. Juniper saplings exhibited improved water status and water use efficiency in response to overstory mortality, whereas piñon saplings did not. Additionally, both piñon and juniper saplings exhibited increased photosynthetic rates, increased photosynthetic capacity, and …
Thermoregulation In Nocturnal Volant Endotherms Occupying Hot Deserts, William A. Talbot
Thermoregulation In Nocturnal Volant Endotherms Occupying Hot Deserts, William A. Talbot
Biology ETDs
The study of thermoregulation is of growing concern in this era of rapid climate change. Earlier studies such as those pioneered by Scholander and Bartholomew directed focus toward the study of endotherm survival in conditions of cold weather adversity. As techniques evolved in the measurement of parameters quantifying thermoregulation, metabolism and energy allocation, the standardization procedures has increased the comparability of data from diverse taxa. We can now search historical records and current research for explanations to the changes in the distribution, migration, extirpation or survival of animal and plant populations through time. It is increasingly common to observe dramatic …
Resolving The Paradox Of Polyploidy: Underexplored Facets Of Polyploid Plants, Benjamin P. Gerstner
Resolving The Paradox Of Polyploidy: Underexplored Facets Of Polyploid Plants, Benjamin P. Gerstner
Biology ETDs
Polyploidy, or whole genome duplication, is a common phenomenon in plants, but the establishment and persistence of mixed-ploidy populations remains a paradox. This dissertation explores factors that contribute to the persistence and establishment of mixed-ploidy populations in nature. The first chapter investigates the role of unreduced gametes in neopolyploid establishment and finds that variability in their formation rate can have a significant impact on polyploid establishment and persistence. The second chapter searches for evidence of soil microbes exhibiting ploidy-specificity, a pre-condition for microbe-mediated niche differentiation, a possible stabilizing mechanism contributing to ploidy coexistence. Finally, the third chapter tests for microbe-mediated …
The Third Domain Of T Cells In The Evolution Of Novel Immune Cell Types, Kimberly Anne Morrissey
The Third Domain Of T Cells In The Evolution Of Novel Immune Cell Types, Kimberly Anne Morrissey
Biology ETDs
αβ and γδ T cells play an essential role in the adaptive immune response and are present in the majority of jawed vertebrates. The T cell receptor (TCR) structure and genetic organization have been generally stable throughout 400 million years of gnathostome evolution. However, the TCRδ chain has displayed degrees of plasticity unseen in other TCR isoforms. One such form appears to be a chimera of a TCR chain with an antibody-like binding domain, known as VHδ and has been found a wide array of vertebrates including cartilaginous fish, coelacanths, amphibians, tuataras, birds, crocodilians, and monotreme mammals. Another, more extreme …
Investigating The Costs And Benefits Of A Nutritional Fungal Endosymbiont, Nolan L. Perryman
Investigating The Costs And Benefits Of A Nutritional Fungal Endosymbiont, Nolan L. Perryman
Biology ETDs
Research on insect symbiosis is dominated by insect–bacteria models, however, the role of fungal symbionts in insects is poorly understood. Fungi are de novo synthesizers of many essential nutrients, therefore, insect–fungal pairings can permit specialization on nutritionally deprived diets. Here, I address the costs and benefits of symbiosis using a system of beetle–fungal symbiosis. Specifically, I ask 1) when reared on a low-quality diet, does the beetle increase the number of viable symbionts to compensate for a heightened nutritional demand, and 2) Is the conferred fitness benefit of the symbiont only present in low-quality diets? When reared on low-quality diets, …
Phylogeographic History Of The Leaf-Eared Mouse, Phyllotis Xanthopygus Complex, Tabitha R. Mcfarland
Phylogeographic History Of The Leaf-Eared Mouse, Phyllotis Xanthopygus Complex, Tabitha R. Mcfarland
Biology ETDs
Museum collections provide essential biodiversity sampling needed to understand the species limits, phylogeny, and biogeographic history of mammals, all key features of the foundation for comparative analyses in ecology and evolution. We add to this framework a diverse assemblage of species of leaf-eared mice (genus Phyllotis) in South America and then focus on the Phyllotis xanthopygus complex by combining available mitochondrial sequence (cytochrome b; cytb) data (351 GenBank samples) with 52 newly sequenced museum samples from the northern extent of this complex’s range (51 from Bolivia and 1 from northern Chile) to reconstruct evolutionary relationships using maximum …
The Effect Of Shrub Cover On Conifer Water-Use Patterns, Growth, And Response To Climate Change In The Southern Sierra Nevada, Marissa Goodwin
The Effect Of Shrub Cover On Conifer Water-Use Patterns, Growth, And Response To Climate Change In The Southern Sierra Nevada, Marissa Goodwin
Biology ETDs
As wildfires increase in size and severity, large areas of forest are undergoing substantial increases in shrub cover. In forests where water is the limiting resource, the partitioning of soil water between shrubs and trees may determine how shrubs affect tree growth and water-stress. We analyzed the δ2H and δ18O values of xylem water for two conifer species (Abies concolor and Pinus jeffreyi) and two shrub species (Arctostaphylos patula and Ceanothus cordulatus) to assess how shrub cover affects the water-uptake patterns of conifers in the southern Sierra Nevada. We found that growing …
Multi-Factor Disturbance Regimes Drive Soil Fungal Community Composition Across A Southwestern Us Riparian Cottonwood Landscape, Rich Wagner
Biology ETDs
In southwestern US riparian cottonwood forests, anthropogenic changes have replaced the structuring force of seasonal flooding with novel multi-factor disturbance regimes, driving these ecosystems to new states. While the impetus for restoration is high, little attention has been paid to understanding belowground feedbacks from these new drivers. Using high-throughput sequencing of environmental DNA, we compared the impacts of fires, exotic plants, restoration practices and lower levels of disturbance on soil fungal community composition and diversity across a riparian cottonwood landscape in New Mexico. We focused on mycorrhizal fungi for the benefits they may confer upon cottonwoods. We found that along …
Transcriptional Regulation Of Stem Cell Function In The Drosophila Central Nervous System, Amalia S. Parra
Transcriptional Regulation Of Stem Cell Function In The Drosophila Central Nervous System, Amalia S. Parra
Biology ETDs
Development of multicellular organisms depends on coordination of various molecular mechanisms to ensure proper tissue size and structure. This is accomplished through intrinsic and extrinsic cues that regulate cell growth and proliferation both spatially and temporally. These well-coordinated signals are present from early developmental stages and remain active throughout development to ensure tissue structure is appropriate for function. This is particularly important in early cell types that form specialized lineages such as stem cells or those found throughout the body such as epithelia. While much progress has been made in understanding growth regulatory mechanisms, several fundamental aspects remain unknown. This …
Transcriptional Silencing Of Cdk18 And Its Role In Lung Carcinogenesis Of Brg1-Mutant Lung Cancers, Loryn M. Phillips
Transcriptional Silencing Of Cdk18 And Its Role In Lung Carcinogenesis Of Brg1-Mutant Lung Cancers, Loryn M. Phillips
Biology ETDs
BRG1 is mutated in 10% of lung cancers, making this mutation clinically relevant. The downstream effects of BRG1 included significantly affecting the cell cycle control and chromosomal replication pathway. CDK18, a cyclin-dependent kinase, was determined to be the gene with significantly decreased expression (p < 0.0001) in the cell cycle control and chromosomal replication pathway. CDK18 is active during the S-phase of the cell cycle and required for genomic stability. Studies were conducted to determine the epigenetic mechanisms that contributed to the repression of CDK18. Histone methylation contributes to the repression of CDK18, and histone deacetylation globally regulates expression of CDK18, while cytosine methylation was found to not contribute to CDK18 expression. Studies were performed to elucidate CDK18 functional role lung carcinogenesis and the genome-wide impact of CDK18 repression. Repression of CDK18 affects cell migration, proliferation, cell-cell signaling, and anchorage-independent growth that contribute to cancer initiation and progression.
Ontogeny Of Sleeping Behaviour In Four Solitary Species Of Anolis Lizards, Joseph C. Barnett, Steven Poe
Ontogeny Of Sleeping Behaviour In Four Solitary Species Of Anolis Lizards, Joseph C. Barnett, Steven Poe
Biology ETDs
Despite the nearly ubiquitous nature of sleep in the animal kingdom, behavioural research on sleep has focused on a few model organisms and widespread behaviours studied in artificial laboratory settings. In this study, we examine the ontogeny of sleeping perch selection in four closely related species of arboreal lizard in situ. The study species each occupy similar habitats and share "solitary" ecology wherein potential lizard competitors are absent, thus providing four partially independent replicates with which to test hypotheses. We find that structural niche, analysed as perch height, varies by age and sex. Males sleep higher than females and adults …
Heat Stressed Exercise Elicits Shifts In Cooling Strategies Across Body Mass In Tropical Songbirds, Kristen Dee Oliver
Heat Stressed Exercise Elicits Shifts In Cooling Strategies Across Body Mass In Tropical Songbirds, Kristen Dee Oliver
Biology ETDs
In resting animals, water use positively correlates with metabolic rate, for example smaller animals using proportionally more water per gram of body mass. However, animals also must endure heat and exertion, and evaporative cooling requires additional water use that may not scale similarly with body size. How evaporative water loss allometrically scales with body mass during heat-stressed exercise is poorly resolved, particularly for birds, yet is critically important for understanding the consequences of climate warming on the fitness of bird populations. Here, we evaluated how air temperature (Ta) influenced evaporative water loss during exercise (EWLexercise) across …
Sensitivites Of Dryland Mammals To Mean And Variance In Aridity, Jessica C. Johnson
Sensitivites Of Dryland Mammals To Mean And Variance In Aridity, Jessica C. Johnson
Biology ETDs
An important component of evaluating the consequences of climate change is to understand not only how climate trends, such as warming, affect species abundance but also how increasing climate variability will change population abundances. Studies on species' sensitivities to interannual variability are rare because they require long-term data collected either over naturally variable climate conditions or within direct manipulations of year-to-year variability. Physiology, functional traits, and diet composition related to resource acquisition or reproduction may be valuable predictors of species sensitivities to changes in both climate mean and variability. We predicted that species with certain physiologies, such as large body …
Combining Isotopic And Genetic Analyses To Quantify Microbial Facilitation Of Recalcitrant Resource Use By Terrestrial And Aquatic Consumers, Alexi Christina Besser
Combining Isotopic And Genetic Analyses To Quantify Microbial Facilitation Of Recalcitrant Resource Use By Terrestrial And Aquatic Consumers, Alexi Christina Besser
Biology ETDs
Quantifying the flow of energy and nutrients through food webs is foundational to understanding the structure and function of ecosystems. Here, I utilize the stable carbon and nitrogen isotope analysis of individual amino acids to trace the movement of essential amino acids through terrestrial and freshwater food webs in New Mexico, USA. I first explore isotopic patterns among co-occurring terrestrial plants and aquatic algae. I then combine this molecular isotopic approach with 16S and 18S rRNA sequencing to demonstrate the importance of gut microbiota as sources of essential amino acids to wild mammalian hosts. Next, I explore the roles of …
Evaluating Microneedle Impedance For Monitoring Water Potential In Vitis Vinifera And Helianthus Annuus, Erica Grace Pauer
Evaluating Microneedle Impedance For Monitoring Water Potential In Vitis Vinifera And Helianthus Annuus, Erica Grace Pauer
Biology ETDs
Measurements of plant water potential provide fundamental insights into how plants are interacting with the environment to manage water needs. However, monitoring water potential is difficult, time consuming, and frequently destructive. Several methods have been in development that attempt to monitor the water status of plant tissues in a simple, continuous, and non-destructive manner. One of these methods, electrical impedance spectroscopy (EIS), is emerging as a particularly promising tool that has several applications in plant biology. I used a new microneedle system that applies small electrodes to a range of tissues. By utilizing this tool in conjunction with a standard …
Unraveling The Complex Interactions Between Members Of The Schistosoma Haematobium Group And Bulinus Snails In And Around Lake Victoria In West Kenya, Caitlin Raiselle Babbitt
Unraveling The Complex Interactions Between Members Of The Schistosoma Haematobium Group And Bulinus Snails In And Around Lake Victoria In West Kenya, Caitlin Raiselle Babbitt
Biology ETDs
Schistosoma haematobium, the agent of urogenital schistosomiasis, and related schistosomes are transmitted by members of the genus Bulinus. Each of the 38 Bulinus species vary in their ability to vector schistosome species and non-schistosome trematodes resulting in a patchwork of snail-parasite compatibilities. Accurately identifying snail intermediate hosts and the disease-causing parasites they transmit is critical for snail control strategies and the management of human schistosomiasis. Towards these ends, this thesis identifies bulinid species and the parasites they transmit and implicates certain species in the transmission of S. haematobium. The thesis also includes a systematic review of methods …
Plant Responses To Drought In A Semiarid Grassland: An Isotopic Approach, Elizabeth V. Fain
Plant Responses To Drought In A Semiarid Grassland: An Isotopic Approach, Elizabeth V. Fain
Biology ETDs
Dryland ecosystems are facing unprecedented climate extremes as a result of global climate change. Water is the most limiting factor in dryland ecosystems, therefore plants in drylands have developed crucial water-use strategies for drought survival. It is important to understand plant physiological responses to water stress as drylands are projected to experience more frequent, severe droughts in the coming decades. To test how plants respond to drought in a semiarid grassland, we measured δ13C, δ15N, and C/N ratio of common C3 and C4 plants (Bouteloua gracilis, B. eriopoda, Pleuraphis jamesii, Salsola tragus, Machaeranthera pinnatifida, …