Biology Commons^™

Can A Sex Bias Be A Good Thing: Modeling Spontaneous Clearance And Sexual Susceptibility In Hcv, Tanner K. Shea

Biology ETDs

Hepatitis C virus (HCV) is a global epidemic that has been increasing for decades, afflicting millions of people who inject drugs (PWID) and is a major cause of liver disease. With novel direct-acting antivirals, treating the virus has become possible yet elimination remains out of reach. Prior research has shown significant differences in disease progression between men and women. These differences can lead to variation in incidence or what proportion of infections progress to chronic infections. We develop a mathematical model that accounts for potential differences between the sexes to evaluate the impacts on HCV transmission. We find that susceptibility …

Chronic And Acute Respiratory Pathogens: Evolutionary And Epidemiological Characteristics Of Tuberculosis, Influenza-Like Illness, And Covid-19, Julie Allison Spencer

Biology ETDs

Tuberculosis and influenza-like illness cause major disease burden for humans. In our first study, we conducted a pangenome analysis of 67 Mycobacterium tuberculosis genomes from Peru. We supported the paradigm that M. tuberculosis is highly clonal; however, a small amount of genetic diversity originates from infrequent recombina- tion events. In our second study, we reviewed the literature for parameters of five common viruses that contribute to influenza-like illness: influenza, RSV, rhinovirus, human coronavirus, and adenovirus. We found that their epidemiological parameters vary considerably, and can have broad ranges; their basic transmission rates are the most important for model outcomes. When …

Plant Litter Decomposition Differs With Species And Soil Resources In A Chihuahuan Desert Grassland, Andrea Lopez

Biology ETDs

Uncertainties surround the extent to which diversity can mitigate the effects of climate change and anthropogenic activity on ecosystem functions. In desert grasslands, changes to water availability and soil nitrogen, two primary resources that limit ecosystem processes, can have lasting impacts on nutrient cycling. We used grass litter from Bouteloua eriopoda, Bouteloua gracilis, Pleuraphis jamesii, and Sporobolus spp. to assess the effects of soil resources on single- and multi-species decomposition in a Chihuahuan Desert grassland in central New Mexico, USA. Litterbags were deployed in a factorial experiment that manipulated rain pulse size (5- vs. 20-mm) and frequency …

Evolutionary Ecology Of Host-Parasite Relationships: Role Of Host Ecology, Phylogeny, And Demographics In Shaping Parasite Evolution, Erika Taylor Gendron

Biology ETDs

Host-parasite systems exist across complex and ecologically heterogeneous landscapes, and may occur across taxonomically and ecologically disparate host species. Under these conditions, mechanisms underlying microevolutionary processes (i.e. gene flow, genetic drift) are not always clear, and may be mediated by numerous co-occurring factors specific to individual hosts. Host traits such as host immunology, demographics, phylogeny and ecology may act in concert to shape host-parasite relationships, and ultimately evolutionary processes. The research described herein used phylogeographic, phylogenomic, and population genetic methods to further understanding of how host traits impact the evolutionary ecology of trematode systems, using avian schistosomes (Digenea: Schistosomatidae) as …

Driver Of Avian Haemosporidian Diversity And Host Specificity In The Solomon Islands, Xena Marie Mapel

Biology ETDs

Avian haemosporidians are protist parasites that are distributed worldwide. We investigated these parasites in a tropical South Pacific archipelago to answer two questions: 1) Which community characteristics influence haemosporidian diversity; 2) Does host specificity vary across islands? To answer these questions we sequenced a mitochondrial gene and created linear models to establish relationships between select variables and diversity. In addition, we calculated host breadth of each lineage and constructed models to infer predictors of diversity. The percent of infected individuals on each island was correlated with island area. Haemosporidian phylogenetic diversity on a given island was associated with the proportion …

A Landscape On The Threshold Of Change: Patterns Of Soil Microbial Ecology Along Dynamic Geomorphic And Hydrologic Features In A Polar Desert, Kelli L. Feeser, David James Van Horn, Heather N. Buelow, Daniel R. Colman, Theresa A. Mchugh, Jordan G. Okie, Egbert Schwartz, Cristina D. Takacs-Vesbach, Becky A. Ball, Andrew G. Fountain, Michael N. Gooseff, Joseph S. Levy, Maciej K. Obryk

Biology ETDs

The McMurdo Dry Valleys (MDV) of Antarctica are on the threshold of widespread landscape scale change due to increasing temperature and solar radiation and altered hydrology: buried ice is melting, the soil active layer is thickening, thermokarst features are developing along streams, water tracks are expanding, and lake levels are rising. These changes will impact the microbial communities found in each of the affected habitats. The purpose of this work is to first, understand the spatial distribution of soil bacteria in the MDV, specifically investigating the scale-dependent effects of environmental heterogeneity, and second, to perform surveys and coupled experiments to …

Reconstructing Energy Flow Through Modern And Historical Marine Communities: Insights From Amino Acid Isotope Analysis, Emma A. Elliott Smith

Biology ETDs

The fundamental currency of life is energy. Organisms need energy to grow, to survive and to reproduce. Understanding the acquisition of energy by consumers is thus a foundational aspect of biological research. This is especially important in the modern era, as impacts of ongoing anthropogenic effects will be mediated or amplified through food webs. Here, I explore how isotopic analysis of individual amino acids – a technique new to ecological studies – can be used to trace energy flow through animal communities in modern and ancient time periods. In particular, I focus on kelp forest food webs, which are nearshore …

Diversification And Biogeography Of An Indo-Pacific Bird Radiation (Pachycephalidae), Serina S. Brady

Biology ETDs

The utility of islands as natural laboratories of evolution is exemplified in the patterns of differentiation in widespread, phenotypically variable lineages. Pachycephalidae is one of the most complex avian radiations spanning the vast archipelagos of the Indo-Pacific, making it an ideal group to study the patterns and processes of diversification on islands. Here, we present a robust phylogenetic hypothesis for all five genera within Pachycephalidae, based on thousands of ultraconserved elements (UCEs) generated with a target-capture approach and high-throughput sequencing. We clarify certain taxonomic relationships within Pachycephala and discover that Wallacea plays a much larger role in pachycephalid evolutionary history …

Dynamics Of Avian Elevational Ranges Reveal Hidden Evolutionary Forces, Chauncey R. Gadek

Biology ETDs

The distribution of life across the Andes mountains reflects historical elevational-range contraction and expansion. Whereas contraction implies specialization, expansion requires overcoming hidden barriers. Three eco-evolutionary phenomena may drive patterns in rates of elevational range evolution: (1) The Dobzhansky-MacArthur Phenomenon (DMP) predicts lower rates of upward expansion with harsher physical conditions, while downward expansion increases with lower diversity; (2) the evolutionary tendency toward specialization predicts contraction increases when ranges are broad; and (3) natural selection for respiratory performance could suppress expansion across mid-elevations due to gene-environment mismatch. We modeled elevational range shifts of Neotropical landbirds. Contrary to the DMP, upward expansion …

A Comparison Of Cave Microbial Communities To Cave Roosting Bat Microbiota In El Malpais National Monument, Usa, Nicole A. Caimi

Biology ETDs

The arrival of white-nose syndrome (WNS), a devastating fungal disease, has highlighted the need to better understand bat microbiota and how bats acquire their microbiota. To address this need, we investigated how bat microbiota compare to microbiota from the cave walls in two El Malpais National Monument caves. The external surfaces of six roosting bats from each cave, representing four different bat species, and their associated microbial mats were sampled. One to three air samples were taken in each cave. Samples were sequenced using Illumina MiSeq sequencing of the 16S rRNA gene for bacterial diversity and the ITS region for …

Mixing It Up: The Impact Of Episodic Introgression On The Evolution Of High-Latitude Mesocarnivores, Jocelyn P. Colella

Biology ETDs

At high latitudes, climatic oscillations have triggered repeated episodes of organismal divergence by geographically isolating populations. For terrestrial species, extended isolation in glacial refugia – ice-free regions that enable terrestrial species persistence through glacial maxima – is hypothesized to stimulate allopatric divergence. Alternatively, upon glacial recession, divergent populations expanded from independent glacial refugia and often contacted other diverging populations. In the absence of reproductive isolating mechanisms, this biogeographic process may trigger hybridization and ultimately, gene flow between divergent taxa. My dissertation research aims to understand how these episodic periods of isolation and contact have impacted the evolution of high latitude …

Role Of Host Cell Β-Catenin During Toxoplasma Gondii Infection, Cameron H. Ranken

Biology ETDs

The microbial pathogen Toxoplasma gondii is an intracellular protozoan that actively invades host cells and simultaneously creates a specialized parasitophorous vacuole within which the parasite lives and replicates. The parasite molecular machinery that drives establishment of the intracellular niche is relatively well known. However, it is now emerging that Toxoplasma exploits less well-understood host cell components to enable successful infection. Here, we examined the role of host Wnt/β-catenin during T. gondii infection. Using human fibroblasts and a mouse dendritic cell line, we found that infection with Toxoplasma stimulated both upregulation and nuclear localization of β-catenin. Using a transwell experimental approach, …

Ecological And Morphological Response Of Rodents To Environmental Change Over The Late Quaternary, Catalina Tomé

Biology ETDs

The rapid progression of modern climate change is already altering ecosystems worldwide. By employing the fossil record, we can investigate how animals responded to past climatic changes and biodiversity loss. The paleontological record of the late Quaternary (past ~22000 years) encompasses a period of considerable environmental change in North America. Rising temperatures and climatic fluctuations are coupled with the extinction of the majority of large bodied mammals on the landscape. The combination of climate and extinction events led to changes in vegetation and community structure which likely affected the resources available and interactions between the remaining mammals within communities. Here, …

Forty Years Of Change In Southwestern Bee Assemblages, Catherine Cumberland

Biology ETDs

Changes in a regional bee assemblage were investigated by repeating a 1970s study from the U.S. Southwest of bees visiting native sunflower (Helianthus annuus). Results showed declines in abundance and species richness of native bees and increases in non-native Apis mellifera. Climate data indicate drought increased over the 40-year period, favoring introduced and generalist species. Experimental placement of A. mellifera in an area of low A. mellifera density in New Mexico reduced native bee visitation, but improved reproduction in H. annuus plants. Meta-analytic models comparing pollination effectiveness in specialist versus generalist, native versus non-native, and native pollinators …

Fungi In A Hot, Dry, Changing World, Miriam I. Hutchinson

Biology ETDs

My doctoral work focused on understanding the reciprocal relationship between fungi and their environment, namely how fungi respond to environmental flux, as well as how fungi can modify and structure their habitats, especially in the context of climate change. As such, I aimed my research on fungi with distinct adaptations to their environmental niches: endophytic fungi that inhabit plant tissue and thermophilic fungi that are capable of growing at the upper temperature limit for eukaryotic life. My research consisted of three studies. First, I investigated the thermophilic species Myceliophthora heterothallica to demonstrate its use as a model organism for efficient …

Warming Up: Climate Change Related Shifts Of Mycorrhizal Fungal Communities In High Latitude Ecosystems, Megan Rae Devan

Biology ETDs

This dissertation examines how climate change affects mycorrhizal fungal communities in boreal and arctic ecosystems. In chapter one, I revealed that increases in fire severity and related increases in deciduous tree dominance result in greater Ascomycota relative abundance (RA) and subsequent declines in Basidiomycota RA. In chapter two I analyzed the effects of post-fire mycorrhizal fungal communites on host growth. There were trends at the fungal genus level that were largely reflected at the guild level across all hosts; however, there were some fungal genera that had the opposite effect on different host species. In chapter three, I found host …

Biogeographical Implications Of Climate Change For An Alpine Mammal, The American Pika, Marie Louise Westover

Biology ETDs

Anthropogenic climate change has already impacted a majority of species globally. The aim of this dissertation is to understand how climate and climate change influences animal ecology and evolution across space and time, using the American pika (Ochotona. princeps) as a model system. I investigate how pika body size, diet, and occupancy are influenced by different aspects of climate over space and time. Body size in O. princeps populations best correlates to precipitation and vegetation, rather than temperature. Our findings suggest that pika body size may be more related to vegetation and food availability than the direct effects …

Ecophysiology Of Ponderosa Pine Seedlings After Severe Fire: The Effect Of Tree Canopy, Lauren Michele Bansbach

Biology ETDs

Ponderosa pine forests evolved with low-severity surface fires to maintain forest structure and process. However, increasingly common high-severity fires often result in complete overstory canopy loss and a shift from forest to shrub- and grass-dominated vegetation that may persist as an alternate stable state due to limited rates of ponderosa seedling regeneration in severely burned areas. Though overstory tree canopy is an important driver of understory plant response, little is known about how the absence of tree canopy following severe fires interacts with changes in year-to-year climate to affect the physiological function of ponderosa pine seedlings. This field study tested …

Riparian Vegetation In The Face Of Environmental Variability, Kelly A. Steinberg

Biology ETDs

Riparian ecosystems are among the most highly disturbed ecosystems globally, over the past century dryland riparian forests have become less likely to flood, removing the largest historical disturbance. Yet these provide many essential ecosystem services. Climate change adds further change and uncertainty to the future of these ecosystems. In the southwestern United States, climate models predict changes in the mean and variance of temperature and precipitation. Determining the ecological consequences of interactions between slow changes in long-term climate means and amplified variability in climate is an important research frontier in plant ecology. We used long-term plant cover, groundwater and precipitation …

Mechanisms Of Oriented Cell Division And Their Roles In Tissue Development, Evan Blake Dewey

Biology ETDs

Properly executed cell division is crucial to development, maintenance, and longevity of multicellular organisms. Defects in both symmetric and asymmetric divisions can lead to improper developmental patterning, as well as genomic instability, disruption of tissue homeostasis, and cancer. Our research focuses on how regulators orchestrate proper cell divisions. Mushroom Body Defect (Mud) is one such regulator, and here we describe how Mud is regulated via the Hippo signaling pathway kinase Warts (Wts), showing Wts phosphorylates Mud to enhance interaction with the polarity protein Partner of Inscuteable, promoting spindle orientation activity. We next focus on another regulator, Shortstop (Shot), describing a …

King Of The Hill? How Biotic Interactions Affect Biogeographical Pattern And Species Responses To Climate Change, Joshua Scott Lynn, Jennifer A. Rudgers, Tom E. X. Miller, Stephanie N. Kivlin, Melanie R. Kazenel

Biology ETDs

As climate has warmed, many species have moved up mountains as physiological limits to their distributions have ameliorated. These distribution shifts are creating novel communities, begging the question: What happens to species at the tops of mountains as potential antagonists encroach upwards? Theory predicts that upward migrations will cause range contractions for high-elevation species because of novel interactions with encroaching antagonists. My dissertation work is one of the most comprehensive tests of this question to date, using a combination of ecological niche modeling (ENM), experiments, and demographic and trait-based modeling approaches. I created novel ENMs that suggest context-dependency of biotic …

Genomics Based Approaches To Fungal Evolution, Aaron J. Robinson, Donald O. Natvig

Biology ETDs

Advances in DNA sequencing and data analysis make it possible to address questions in population genetics and evolution at the genomic level. Fungi are excellent subjects for such studies, because they are found in diverse environments, have short generation times, can be maintained in culture and have relatively small genomes. My research employed genetic approaches using a variety of sequencing technologies and methods of analysis to explore questions in fungal evolution.

In one study, I explored the genetics behind differences in thermotolerance between isolates of Neurospora discreta from Alaska and New Mexico. Isolates from the two states exhibited differences in …

The Evolution Of Diet Breadth In Melissodes Bees (Apidae: Eucerini), Karen W. Wright

Biology ETDs

The relationship between phytophagous insects and their host plants has interested scientists since Darwinian times. Using modern phylogenetic inference, we are able to investigate these patterns using, not only the phylogenies of the insects, but the evolutionary relationships among the plants they feed on as well. The relationships between bees and the plants they pollinate were traditionally seen as mutualistic and were treated separately from the research investigating the antagonistic relationships between phytophagous insects and their host plants. However, recent phylogenetic studies have made great progress including bee-host relationships in with the larger body of work on phytophagous insects.

The …

Shedding Light On The Role Of Opaque1 In Asymmetric Cell Division In Maize, Janette Yuseil Mendoza

Biology ETDs

Asymmetric cell division (ACD) is important for cell fate and tissue patterning. Many aspects of ACD in plants, however, are still unclear. The process of ACD can be broadly broken down into three phases: (1) cell polarization, (2) division plane establishment and maintenance, and (3) cell division and cytokinesis. Stomatal development in maize has proven to be a useful model for understanding the ACD mechanism. Previous studies have identified several proteins important for all three phases of ACD. Actin is important in each of the phases of ACD, suggesting an actin motor such as myosin may also be important for …

Physella Acuta, Comparative Immunology And Evolutionary Aspects Of Gastropod Immune Function, Jonathan H. Schultz

Biology ETDs

Gastropod immunobiology has benefitted from investigations focused on the planorbid snail Biomphalaria glabrata, intermediate host for the human parasite Schistosoma mansoni. Though such concentrated efforts have elucidated fascinating aspects of invertebrate immunity, they have not provided full knowledge regarding the evolution of immune function among other gastropod species. This dissertation presents the importance of making strategic choices regarding which organisms to select for comparative immunology. Herein, the choice was made to investigate the immunobiology of Physella acuta, a freshwater snail species of the Physidae, a sister family to Planorbidae to which B. glabrata belongs. Benefiting greatly from …

Towards A Better Understanding Of The Effects Of Praziquantel On The Interaction Between The Helminth Parasite Schistosoma Mansoni And Its Murine Host, Melissa Catherine Sanchez

Biology ETDs

Schistosomiasis is a neglected tropical disease (NTD) that infects 206 million individuals worldwide. This disease is caused by dioecious trematodes of the genus Schistosoma, and its pathology is associated with the large number of eggs that are released by the female. Entrapped eggs lead to host immune and inflammatory responses resulting in disease progression. Chemotherapy provides the main means of control and praziquantel (PZQ) is the only widely available drug that is used in all mass drug administration (MDA) programs. As the number of individuals receiving PZQ continues to grow, the development of PZQ resistance is a concern and …

Avian Thermoregulation In The Heat: Resting Metabolism, Evaporative Cooling And Limits To Activity In Sonoran Desert Birds, Eric Krabbe Smith

Biology ETDs

Birds in subtropical deserts face significant thermoregulatory challenges as environmental temperatures regularly exceed avian body temperature. To understand the differing susceptibility of desert birds to increasing temperatures, this dissertation initially examined thermoregulatory performance in seven passerine bird species varying in body mass from 10 to 70g – Lesser Goldfinch, House Finch, Pyrrhuloxia, Cactus Wren, Northern Cardinal, Abert’s Towhee and Curve-billed Thrasher – and three larger Sonoran Desert nesting bird species – Mourning Dove (104 g), White-winged Dove (147 g) and Gambel’s Quail (161 g). Daytime resting metabolism, evaporative water loss and real-time body temperature were measured using flow-through respirometry at …

Intraspecific Floral Color Variation As Perceived By Pollinators And Non-Pollinators: Evidence For Pollinator-Imposed Constraints?, Kellen Cedar Paine

Biology ETDs

Pollinator-mediated selection is expected to constrain floral color variation within plant populations, yet populations with high color variability are common in nature. To explore this, we collected floral reflectance spectra for 34 populations of 14 plant species of New Mexico, USA, and translated them into three different visual spaces. We found evidence that the majority comparisons were indistinguishable to bees, the dominant pollinator group. We also found that floral color variation was significantly greater for two non-pollinating groups, birds and humans. Our results suggest that a portion of human-perceived floral color variation within populations persists because it is invisible to …

Hemocyanin-Like 1 Protein, Unique To Planorbid Snails, Supports Reproductive Output Of Biomphalaria Glabrata, Vector Of Schistosomiasis, Janeth Julieta Peña

Biology ETDs

The Neotropical freshwater snail, Biomphalaria glabrata is a major intermediate host of the parasite Schistosoma mansoni, causative agent of human intestinal schistosomiasis. Disease control efforts consist mainly of mass drug treatment but it is recognized that targeting of the snail vector is essential to prevent parasite transmission that leads to rapid (re)infections. This dissertation combines the knowledge of basic snail biology with modern molecular techniques including protein analysis, next-generation sequencing, proteomics, qRT-PCR and RNA interference to: (1) characterize hemocyanin-like genes in B. glabrata, in particular with further description of the egg mass fluid (EMF) protein hemocyanin-like 1 (Hcl-1), (2) …

The Fate Of Xylem-Transported Co2 In Plants, Samantha S. Stutz, David T. Hanson

Biology ETDs

The concentration of carbon dioxide in tree stems can be ~30-750 times higher than current atmospheric [CO2]. Dissolved inorganic carbon enters the xylem from root and stem respiration and travels with water through the plant. However, the fate of much of this xylem-transported CO2 is unknown. In these studies I examined the fate of xylem-transported CO2 traveling through the petiole and leaf. This was accomplished by placing cut leaves from a woody and herbaceous C3 species, and a Kranz-type C4 species, in a solution of dissolved NaH13CO3 at concentrations similar to those measured in nature. This allowed me to track …