BIO Theses

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    Plastic responses to diet quality and thermal gradients in dung beetles
    (Wichita State University, 2024-05) Proctor, Max Ryu; Jameson, Mary Liz
    In a dynamic world, organisms must swiftly adapt to environmental changes. Phenotypic plasticity enables organisms to alter their traits within their lifetime, providing a rapid response to shifting environments. Dung beetle horns display extreme plasticity, with males exhibiting varying horn sizes (horned "major" to hornless "minor" morphs) based on larval diet (dung type). Horns are utilized in male-male contests for mating, and body and horn size strongly influence success. Though plastic responses to dung quality are well studied, the interplay of temperature and nutritional conditions on these traits remains unexplored. We reared the dung beetle Digitonthophagus gazella in bison (Bison bison) and cattle (Bos taurus) dung, and across seven temperatures (22-34°C) to determine how these environmental factors interact to shape plastic responses in body size and horn length in dung beetles. Almost all (99%) of reared male beetles were major males in both cattle and bison dung treatments, indicating that both dung types are high quality resources for developing dung beetle larvae. The interaction between dung quality and temperature revealed distinct responses: beetles from bison dung show no temperature related changes in body size and horns, while those from cattle dung exhibit larger sizes at intermediate (26-30°C) temperatures compared to those at colder (22-24°C) or warmer (32-34°C) temperatures. This suggests that cattle dung may be a higher quality resource for D. gazella, allowing beetles to utilize a thermal optimum. In addition, development rates increased with temperature, with a more pronounced increase in the bison dung treatment. The interactive effects of diet quality and temperature on morphological and physiological plasticity in dung beetles demonstrate that plastic responses to one factor are not always fixed and can vary with changes in another. To accurately predict how organisms will respond to changing climates, it is essential to evaluate how thermal responses are altered by other factors such as diet quality.
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    The effects of drying-induced trophic cascades on larval salamander development and wetland function
    (Wichita State University, 2024-05) Burkhead, Shania Evelyn Milagros; Luhring, Thomas M.
    Many studies have been conducted on the effects of active drying on amphibian development, however, not much is known on what carry-over effects there may be from previous drying events. Previous drying and density have an interaction effect, with density determining body size of anurans following a drying event. By combining factors of previous drying and densities of the larval salamander, Ambystoma texanum, we will attempt to identify how drought-induced trophic cascades affect the overall development of salamanders and wetland trophic structures. Using mesocosms, we combined 4 density treatments (10, 20, 40, and 80 individuals) with 2 drying treatments (Non-dried and Dried-Refilled) to create 8 treatment combinations (n=64). We recorded larval A. texanum vital rates (e.g., growth, development, survival), (2) odonate abundance and size and (3) gross primary productivity. Previous drying significantly increased survival of larval A. texanum due to the loss of top predators, with only one survivor in the non-dried mesocosms. In dried-refilled tanks, growth and development rate, time to metamorphosis, and size at metamorphosis were negatively correlated with density. Odonates (larval dragonflies) were much smaller following refill and less abundant. GPP was also lower following a refill, however, higher larval salamander densities accelerated GPP recovery and more quickly surpassed GPP of non-dry mesocosms due to top-down control of zooplankton. We found supporting evidence that drying and refilling leads to loss of top-level predators and increasingly strong density-dependent responses of vital rates. Our findings suggest that larval A. texanum require intermittent pools for successful reproduction, and that the carryover effects of drying are not the same for all amphibians. This study highlights the need to understand taxa-specific responses to previously dried pools.
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    Linking plant traits to species performance during early stages of community assembly in a tallgrass prairie
    (Wichita State University, 2023-12) Bethel, Adrian M.; Houseman, Gregory R.
    Linking plants trait to community assembly is an important area of community ecology but quantitative studies are nearly absent from the grassland biome of North America despite the large extent and the high research activity in this region. There are numerous plant trait-performance studies from grasslands that generally report very weak results. I hypothesized that a competitive index based on three key traits (plant height, specific leaf area, plant density) would predict competitive success during community assembly. I tested this idea in a community assembly experiment that included manipulation of soil heterogeneity, seeding patterns, and patch size over a five-year period. I used patch data from treatments where a single species was sown into individual 20x20 cm patches and measured species performance between years 2-5 of the experiment. I found significant relationships between the competitive index in both presence probability and abundance patterns in each year of the analysis. Interestingly, single or combined direct measures of plant traits failed to explain abundance or presence probability. These findings suggest that a competitive index may be a more effective way to link plant traits and community assembly and may offer a promising new approach for trait-plant performance investigations.
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    Effects of follicle-stimulating hormone glycosylation on ovarian follicle development
    (Wichita State University, 2023-12) Cosper, Kirsten Elisabeth; Bousfield, George R.
    Follicle-stimulating hormone (FSH) is a reproductive glycoprotein hormone that exhibits macroheterogeneity in the form of absence or presence of a glycan. Three glycoforms of FSH exist, including FSH18, FSH21, and FSH24, with FSH24 being the least bioactive form of FSH and FSH21 being the most bioactive form. This is physiologically significant, because FSH21 is the dominant circulating form of FSH in young women of reproductive maturity, however, as women approach perimenopause, FSH24 becomes the dominant circulating form. FSH exhibits stage specific functions in regard to ovarian follicle development. This study will measure the expression of two genes, connexin-43 (GJA1), and hyaluron synthase 2 (HAS2). Connexin-43 is upregulated during early stages of follicle development to induce gap junction communication and downregulated during late stages of follicle development to halt gap junction communciation. Hyaluron synthase 2 (HAS2) is upregulated during late stages of follicle development to induce cumulus expansion, a morphological change in the cumulus-oocuyte complex that prepares the oocyte for ovulation. Porcine ovaries were used to isolate cumulus-oocyte complexes and granulosa cells to be used for quantitative real time PCR studies. The cumulus- oocyte complexes and granulosa cells were treated with FSH18, FSH21, and FSH24 and the expression of gap junction protein connexin-43 and cumulus expansion-associated protein hyaluronan synthase-2 were measured and compared to investigate how glycosylation of FSH effects the expression of these vital genes involved in ovarian follicle development.
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    The temporal response of a generalist soil-borne fungal plant pathogen in native grassland communities
    (Wichita State University, 2023-07) Houchen, Barrett Brad; Houseman, Gregory R.
    Soil-borne fungal plant pathogens (SFPP) occupy the soils of ecosystems globally, but the ecology of individual species is often not well understood. One approach to help better understand a SFPP is to examine its temporal variation and response to its environment. Research on SFPP is biased towards agriculture, but many agriculturally important SFPP inhabit adjacent untilled, native systems. One such case is the SFPP Macrophomina phaseolina. Past research has shown that M. phaseolina thrives in soil with high temperatures and low moisture. In untilled grasslands, the presence of this SFPP and its response to seasonal fluctuations in soil temperature and moisture remains unclear. To determine the dynamics of M. phaseolina in untilled systems, I established nine plots within distinct soil types and quantified the monthly response of M. phaseolina to shifting soil temperature and moisture conditions from May 2022 to May 2023. I hypothesized that M. phaseolina density would increase across the growing season, reaching its highest densities in the month of August 2022 when high soil temperatures and low soil moisture would be most favorable. Macrophomina phaseolina density was highly variable among the nine plots during the growing season and seldom reached its highest density during August 2022. During the dormant season, M. phaseolina density markedly decreased to its lowest densities before sharply increasing to unexpectedly high densities in April 2023. These findings suggest that the sporadic variation of M. phaseolina in untilled systems during the growing season contrasts with frequent assertions that soil temperature and moisture will heavily influence this SFPP’s density throughout the year. The results suggest that soil temperature and moisture play a reduced role in untilled systems, as plant community phenology and competing soil antagonists may more strongly impact M. phaseolina growth and disease development.
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