BIO Theses

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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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    Investigating the impacts of drought-related drying events following pond refill on the growth, survival, and postmetamorphic fitness of lithobates blairi tadpoles
    (Wichita State University, 2023-05) Skerlec, Samantha Marie; Luhring, Thomas M.
    The incomplete recovery following drying events can have long-lasting impacts on aquatic ecosystems through altered resource availability, changes to water quality and temperature, microhabitat suitability, and community structure. Dynamic impacts of drying events can have detrimental effects on numerous aquatic organisms, but amphibians are particularly susceptible due to their reliance on aquatic environments for reproduction. This study aims to understand how drying events affect amphibian larval communities that recolonize a pond post-refill by investigating the impacts of incomplete recovery on their growth and development. While similar studies have investigated larval amphibian responses to active drying, few have directly assessed the carryover effects of drying events on organisms that recolonize a previously dried pond. Using a 64-mesocosm array, we examined the effects of drying (non-dry vs. dry-rewet) and tadpole density (10, 20, 40, or 80 individuals per tank) on larval amphibian growth, development, and survivorship. We hypothesized that drying and rewetting would decrease growth and development of tadpoles by reducing food resources, and that high larval densities would decrease growth and development through competition. Our results demonstrate strong effects of past drying on larval amphibian growth, time to metamorphosis, and survivorship. Additionally, we observed carryover effects of larval treatments on juvenile jumping performance, which was influenced by body mass at metamorphosis. Larger juveniles were found to jump further distances on average than smaller individuals, which has implications for the terrestrial fitness of these organisms, including predator evasion, foraging, and mating success. These findings emphasize the importance of drying events for amphibian survivorship and developmental plasticity, and that larval history can determine post-metamorphic fitness.
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    Exploring the effects of cranberry extract on the growth of sinorhizobium meliloti (ensifer meliloti) when paired with known antimicrobial compounds
    (Wichita State University, 2023-05) Denner, Abraham Verschelden; McDonald, David
    Huanglongbing disease (HLB), also known as citrus greening disease, is devastating the citrus industry. It is caused by three species of Candidatus Liberibacter. The presentation of this disease in North America is primarily caused by the asiaticus species. Ca. L. asiaticus is spread by the Asian Citrus Psyllid Diaphorina citri during feeding. Current treatments include broad-spectrum antibiotics, and targeting of the insect vector, both having thus far demonstrated little effectiveness. This has led to our effort to find more suitable antimicrobial substances for this purpose. Finding novel antimicrobials that are effective against Ca. L. asiaticus is essential to combat the spread and severity of HLB. Sometimes, when using antimicrobials together, they can produce a powerful effect that is greater than the sum of the parts; this is known as synergy. By focusing on using candidate antimicrobials in combination in hopes of finding synergistic reactions, one can minimize the potential of antimicrobial resistance forming. As Ca. L. asiaticus cannot be readily cultured in labs, an alternative model must be used. For this research, we used Sinorhizobium meliloti (S. meliloti) as the target bacterium due to its being closely related as well as being more robust due to its free-living capabilities. Cranberries contain phenolic compounds such as proanthocyanidins that can interfere with and repress biofilm formation and alter selective membrane permeability and multidrug efflux pumps. Plant-derived antimicrobials such as methylglyoxal, oregano oil, and clove oil have a variety of antimicrobial mechanisms. This project sought to test these plant-derived antimicrobials in combination with cranberry extract to see if they demonstrated inhibition of growth against the target bacteria. Serial dilutions of cranberry extracts paired with plant-derived antimicrobials were assessed in a checkerboard assay in the presence of S. meliloti. By finding the minimum inhibitory concentrations (MICs) and the fractional inhibitory concentrations (FICs), the level of synergy was determined. While synergy was not demonstrated in this study, two of the plant-derived antimicrobials, methylglyoxal and oregano oil, combined with cranberry extract did prove to be additive. These additive combinations are still beneficial and could be further studied as potential treatment sources or as a basis for further research regarding effective antimicrobial candidates to combat Ca. L. asiaticus based on their mechanisms and efficacy together.
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