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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, …

Above- And Belowground Responses To Environmental Change In The Northern Chihuahuan Desert, Renée F. Brown

Biology ETDs

Drylands cover 45% of the terrestrial surface and are expanding rapidly due to anthropogenic drivers. Altered precipitation regimes, atmospheric nitrogen deposition, and wildfire will likely have significant consequences in these regions where ecological processes are limited by water and nitrogen. In this dissertation, I explored temporal dynamics of net primary production (NPP) and related above- and belowground processes under several environmental change drivers in the Sevilleta National Wildlife Refuge, central New Mexico, USA. Located in the northern Chihuahuan Desert, this region experiences strong seasonal precipitation patterns driven by the North American Monsoon, historically characterized by frequent small rain events hypothesized …

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 …

Low Site-Specific Genomic Variability Is Consistent With The History(S) Of Fragmentation Of The Riparian Biota Of The Arid Southwest, Manuela Londono-Gaviria

Biology ETDs

Persistently low population sizes, when coupled with reduced interpopulation connectivity, can impede the long-term viability of species in fragmented landscapes. Riparian-associated species in the arid American Southwest now face a series of threats due to fragmented populations and changing environmental conditions. During the last century, riparian habitats have deteriorated due to the synergistic effects of livestock grazing, increasing incidence of fire, and other anthropogenic impacts potentially have made local populations smaller, less demographically stable, and susceptible to the negative impacts of genetic drift and stochastic events. We evaluated genomic variation within and across geographic areas (i.e., mountain ranges and river …

Transcriptional Analysis Of Maize Under Drought Stress And The Impact Of Plant Maturity, Oliver J. Oviedo

Biology ETDs

Climate change related drought is projected to harm maize production. Water use strategies can help mitigate the impact of drought on crop yield. However, little is known about maize metabolic response to drought at different developmental stages. To shed light on this, drought conditions were applied to maize at the six-leaf stage (V6), twelve leaf stage (V12), and tassel stage (VT). V6 and VT took eight days to achieve a low stomatal conductance threshold, but V12 took 16 days. Differential gene expression analysis of the transcriptome indicates that V6 showed the most response with 53 impacted metabolic pathways, many of …

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.

Improving Photosynthetic Efficiency In Microalgae Through The Genetic Engineering Of Energy Sensors And Photoreceptors, Taylor L. Britton

Biology ETDs

Through photosynthesis microalgae can convert sunlight, water, and CO₂ into chemical energy that can be used to generate carbon neutral biofuels and biomass. With an ever-increasing demand and need for petroleum substitutes it is imperative that we improve the output of industrial-relevant crops such as microalgae. One important way of improving output in algae is by understanding the roles that stress and energy conversion is regulated in these organisms. Photosynthetic organisms fundamentally depend on light- and sugar-driven metabolic and signaling networks, which integrate environmental cues to govern and sustain growth and survival. SnRKs (SNF1-related protein kinases) and the photoreceptor …

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 …

Keeping Your Cool: Thermoregulatory Performance And Plasticity In Desert Cricetid Rodents, Richard W. Ramirez, Eric A. Riddell, Steven R. Beissinger, Blair W. Wolf

Biology ETDs

Small mammals in hot deserts often avoid heat via nocturnality and fossoriality and are thought to have a limited capacity to dissipate heat using evaporative cooling. Research to date has focused on thermoregulatory responses to air temperatures (T_a) below body temperature (T_b). Consequently, the thermoregulatory performance of small mammals exposed to high air temperatures is poorly understood, particularly responses across geographic and seasonal scales. We quantified the seasonal thermoregulatory performance of four cricetid rodents (Neotoma albigula, N. lepida, Peromyscus eremicus, P. crinitus) exposed to high T_a, at four sites …

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 …