Life Sciences Commons^™

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 …

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 …

Resolving The Paradox Of Polyploidy: Underexplored Facets Of Polyploid Plants, Benjamin 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 …

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 …

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 …

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

Biology ETDs

ABSTRACT

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 …

The Third Domain Of T Cells In The Evolution Of Novel Immune Cell Types, Kimberly Anne Morrissey

Biology ETDs

ABSTRACT 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 …

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

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 …

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 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

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

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 (T_a) influenced evaporative water loss during exercise (EWL_exercise) across …

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 G. 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

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 …

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, …

Olfactory Detection Of Viruses Shapes Brain Immunity And Behavior, Aurora Kraus

Biology ETDs

Olfactory sensory neurons (OSNs) directly contact the environment and are

exposed to pathogens, such as viruses. When OSNs detect a virus, they coordinate antiviral immune responses locally to stop virus progression into the brain, termed the central nervous system (CNS). For example, in COVID-19 patients the SARS-CoV-2 virus replicates in the olfactory epithelium resulting in loss of olfaction, yet viral presence in the CNS is rare. However, neuronal detection of a virus by OSNs may send electrical signals to the CNS via the olfactory bulb (OB) and shape our CNS. Because the OB is the nexus between the pathogen exposed …

Relating Plant Community Structure To Carbon Dynamics In Semiarid Grasslands, Theodore D. Roper

Biology ETDs

Understanding how fine-scale changes in soil characteristics and plant community composition affect ecosystem functioning is key to predicting how biome shifts will affect regional and global carbon cycling. This is crucial in the dryland biomes of the US Southwest, projected to be one of the regions most affected by climate change. We examined fine-scale drivers of ecosystem function within two biomes – a Chihuahuan Desert grassland and Plains/Chihuahuan Desert ecotone – via long-term vegetation data, micrometeorological data, eddy covariance carbon flux measurements, and soil water and texture, finding that the ecotone site had over 30% higher soil water content, over …

Sierra Nevada Mixed-Conifer Regeneration Response To Repeated Burning Varies By Species, Carolina J. May

Biology ETDs

Fire-exclusion has acted as a major perturbation on dry conifer forests, increasing tree density and, in mixed-conifer forests, the dominance of shade-tolerant species. Restoration efforts aim to reverse these effects by reducing stand density, restoring relative proportions of tree species, and reintroducing recurrent fire, but the long-term effects of repeated burning on tree regeneration have not been quantified. We analyzed two decades of seedling and overstory data from the Teakettle Experimental Forest in the southern Sierra Nevada to determine how thinning and repeated burning affect seedling establishment and overstory recruitment. Across treatments, pine seedling densities remained much lower than shade-tolerant …

Thermoregulation And Spatial Distribution Of Lizards In The Southwestern Usa: Adaptation To A Changing Climate, Caleb Lee Loughran

Biology ETDs

Lizards rely heavily on environmental temperatures to thermoregulate and maintain a body temperature (Tb) that optimizes physiological function and maximizes surface activity time. While early research noted the propensity for lizards to thermoregulate by shuttling between different thermal environments, it was long assumed that evaporative cooling via panting was an ineffective means of thermoregulation. However, evaporative cooling can potentially lower a lizard’s Tb significantly below air temperature, and thus allow lizards to extend activity periods during prolonged heat exposure. In this dissertation, I explore the varying abilities of lizards to thermoregulate while panting. I describe the metabolic and evaporative water …

Biodiversity And Global Change In Terrestrial Ecosystems, Timothy J. Ohlert

Biology ETDs

Terrestrial ecosystems are critical to human and ecological processes but many gaps in our knowledge remain regarding how terrestrial plant communities assemble and respond to global change. I used field experiments distributed around the world, including long-term experiments from the Sevilleta National Wildlife Refuge (SNWR) in New Mexico and deserts of the southwestern U.S., to evaluate the consequences of drought and other abiotic stressors on plant communities. Dominant grasses were particularly important for the productivity and structure of grasslands at SNWR. In general, the structure of desert plant communities had high resistance to extreme drought, though grasses and other perennial …

Traits And Functional Diversity Of A Hyperdiverse Bee Assemblage Are Linked To Aridity, Benjamin D. Turnley

Biology ETDs

Climate change in the American Southwest is altering the composition of species assemblages. However, the resulting patterns in mean trait values and functional diversity are poorly understood. Bees assemblages in Southwestern drylands are exceptionally diverse, and vary greatly in their morphologic traits. In this study we focused on two questions: Have community-weighted mean trait values shifted over time and/or with aridity, consistent with the hypothesis that aridification is driving bee assemblage change? Has the functional diversity of the Sevilleta bee assemblage declined over time and/or with aridity, consistent with the hypothesis that pollination services could be declining? To address these …

Ontogenetic Niche Shift As A Driver Of Community Structure And Diversity In Non-Avian Dinosaurs, Katlin Schroeder

Biology ETDs

As some of the most charismatic megafauna to ever walk the earth, the physiology, morphology, growth and evolution of non-avian theropods has been studied exhaustively, yet little is understood about their roles in ecosystems as juveniles. For carnivorous megatheropods, which exceed 1,000kg in mass yet hatched from eggs of limited size, the likelihood of utilizing different prey through ontogeny was high, simply by proxy of the immense difference in size between adults and juveniles. We found these ontogenetic niche shifts, evidenced by significantly different dental microwear in Tyrannosaurids, to have excluded dinosaurian mesocarnivores from Mesozoic communities. The few dinosaurian mesocarnivores …

The Consequences Of Climate Change For Native Bee Assemblages, Melanie R. Kazenel

Biology ETDs

Recent declines in terrestrial arthropod biodiversity highlight the need to pinpoint which taxa and ecosystem services are most threatened, and why. But, for most of the world’s ~20,000 bee species, we lack robust evidence of population trends, and the role of climate change remains surprisingly little studied. I used long-term bee monitoring data from the Sevilleta Long-Term Ecological Research Program (Socorro, NM, USA), along with complementary experimental and observational data, to examine how climate relates to bee abundance and diversity patterns over time and space, and to identify the traits that govern bees’ climate sensitivities.

A Diverse Flea (Shiponaptera) Assemblage From The Small Mammals Of Central New Mexico, Dianne Esther Peterson

Biology ETDs

The geographical ranges of many mammals and their associated parasites are dynamic. Comprehensive documentation of these communities over time provides a foundation for interpreting how changing environmental conditions, driven by accelerating climate change, other anthropogenic disturbances, and natural events may influence host-parasite interactions. Fleas (Order Siphonaptera) are obligate, hematophagous parasites of birds and mammals with medical interest due to their role in transmitting pathogens. From 2016 to 2019, we sampled the small mammal and associated flea communities in El Malpais National Conservation Area (El Malpais) in Cibola County, New Mexico. Among 898 mammalian specimens, 925 fleas representing 29 species were …

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 …

Rapid Source To Sink Transition In A Mixed-Conifer Forest Following Stand-Replacing Fire, Ryan Matthew Schulze

Biology ETDs

Mixed-conifer forests play an important role in the Southwestern USA’s regional carbon cycle by sequestering and storing large amounts of atmospheric carbon onto the landscape. Despite this, little is known about how large, stand-replacing fire alters ecosystem carbon sink-source dynamics. In this study, we used eddy covariance to quantify how stand-replacing fire altered forest sink strength, and the sensitivity of carbon uptake to soil and atmospheric drought in a mixed-conifer forest located in The Valles Caldera National Preserve, NM. We found that the post-burn ecosystem returned to an annual net sink of carbon in the year immediately following the fire, …

Sex- And Age - Specific Migratory Strategies Of Blue Whales In The Northeast Pacific, Christina Blevins

Biology ETDs

Sequential subsampling of blue whale baleen plates can yield information of individual migratory plasticity of this endangered species in the northeast Pacific Ocean. We measured δ13C and δ15N isotope values along baleen from thirteen whales of different age and sex. Results showed sex/age-specific migratory strategies. Adult females exhibited relatively stable cyclical movements between temperate and subtropical regions. Adult males exhibited two strategies, most remained within temperate latitudes, whereas two migrated to subtropical latitudes. Movement patterns in juveniles were erratic. These patterns are potentially driven by energetic requirements of females, intraspecific competitions among adult males, and inexperience in locating prey in …