BIO Graduate Student Conference Papers

Permanent URI for this collection


Recent Submissions

Now showing 1 - 5 of 66
  • Item
    Variation in effect of insect herbivory on Platte thistle (Cirsium canescens) between biogeographic range center and edge
    (Wichita State University, 2020-05-01) Taylor, Mason; Russell, F. Leland
    INTRODUCTION: Insect herbivory can reduce plant fitness and population sizes, but the strength of these effects varies greatly in space. The position of a plant population within the plant species' biogeographic range is an unexplored hypothesis to explain spatial variation in herbivore effects on plants. The Abundant Center Hypothesis (ACH) states that conditions for a species will be poorer at the species' range edge than in the center and, hence, a species will be more abundant toward the range center, and scarcer toward the edge. These hypothesized changes in plant performance and abundance may have implications for the intensity of herbivore attack on plants and plants' abilities to recover from herbivory. Platte thistle (Cirsium canescens) is a monocarpic species whose range is centered in the Nebraska Sand Hills and reaches its western limit in south central Colorado. PURPOSE: This study addresses 1) How do Platte thistle rosette (juvenile thistle) survival, growth, transition to adulthood, and adult seed production differ between range edge and center? and 2) How do the effects of insect herbivory on adult seed production and seedling recruitment differ between range edge and center? METHODS: I address these questions using insect exclusion experiments on reproducing adult Platte thistles and demographic data collection on juvenile thistles at the southwestern range edge of Platte thistle in Colorado. I achieve the range edge -- range center comparison by evaluating overlap of 95% confidence intervals around range-edge and range-center parameter estimates. Range center parameter estimates are available in published literature. RESULTS: Preliminary analyses suggest a positive relationship between the size of juvenile Platte thistle and the likelihood of transition to a reproductive stage. At the southwestern range edge in Colorado, no significant effect of elevation on growth, survival, or transition to a reproductive stage occurred. CONCLUSION: Further data analyses are being performed to reveal any significant differences in effect of insect herbivory on Platte thistle seed production and seedling recruitment between range-edge and range-center.
  • Item
    Ecological succession of the microbial community of a spacecraft assembly facility in enriched brines relevant to Mars
    (Wichita State University, 2020-05-01) Carte, Meris; Schneegurt, Mark A.
    Life detection missions to Mars should be as free of microbial organisms as possible to avoid transporting contaminants on spacecraft surfaces. Any microbes that make the trip to Mars or the round-trip back to Earth may compromise our ability to recognize authentic biosignatures from native Mars organisms. Current planetary protection protocols require that any spacecraft components must be assembled in cleanrooms that have nearly aseptic conditions, reducing the chance of microbial contamination. This current research studies samples from NASA's Jet Propulsion Laboratory Spacecraft Assembly Facility (JPL-SAF), collected from high-traffic surfaces and entryways. Microbes from these samples were enriched in brines representative of Mars' high-salt environment. Through the use of leading-edge molecular genetic techniques, detailed descriptions of the changing microbial communities were made at regular timepoints for up to six months. Over forty bacteria present in the brines after six months of enrichment were isolated, characterized, and identified to determine which microbial strains from JPL-SAF wipes are most likely to survive under the conditions of near-surface Mars. Knowing if microbes from SAFs could potentially survive on Mars informs efforts to protect Mars from microbial contamination that can complicate life detection or harm potential native ecosystems.
  • Item
    The distribution of legume species across the precipitation gradient of Kansas
    (Wichita State University, 2019-04-26) Urban, Abigail; Houseman, Gregory R.
    Legume species are important for fixing atmospheric nitrogen, facilitating nutrient cycling, and increasing plant and habitat diversity, yet the distribution of legumes is not well understood. To examine the distribution of legume species across the precipitation gradient of Kansas, we used the USDA database to quantify how legume species richness varied across the state. Specifically, we related legume species occurrences in each of the 105 counties in Kansas to annual precipitation data and also assessed whether these patterns varied for native and non-native legume species. Legume diversity was strongly correlated with annual precipitation (r2=0.56), as species richness more than doubled across Kansas, increasing from 23 to 54 species. However, this change in legume diversity varied depending on whether legumes were historically native or non-native. We found a sharp increase in the proportion of non-native species as precipitation increased, from 8 to 22%. The significant correlation between the proportion of non-native legume species and precipitation was remarkably high (r2=0.7), suggesting that this pattern is highly reliable across counties in Kansas. These strong patterns suggest that the number and presence of both native and non-native legume species are linked with precipitation regimes in the Great Plains, most likely due to variance in drought tolerance among species. However, additional observational and experimental work is needed to clearly distinguish between the importance of soil properties, land management, and plant community composition on legume distributions across the precipitation gradient of Kansas.
  • Item
    Antimicrobial synergy between cranberry and Manuka honey against dental caries bacteria
    (Wichita State University, 2019-04-26) Prince, Alisha; McDonald, J. David
    INTRODUCTION: Dental caries is caused by dental plaque, which is a community of micro-organisms embedded in an extracellular polymer matrix as a biofilm on the tooth surface. Natural products that are widely accessible could be used as an alternative or adjunctive anti-caries therapy. Sometimes, when two products are used together, they yield a more powerful antimicrobial effect than the anticipated additive effect. These synergistic combinations are often better treatment options because individual agents may not have sufficient antimicrobial action to be effective when used alone. Moreover, the use of two agents simultaneously greatly reduces the development of bacterial resistance. Cranberries contain phenolic compounds like anthocyanidins that disrupt biofilm formation by oral bacteria. Manuka honey has high concentrations of bioactive agents like methylglyoxal, which are cariostatic. Because cranberries and manuka honey have varied modes of antimicrobial action, it is important to test them for possible synergistic effects when they are combined into one treatment. PURPOSE: To determine antibiotic synergy between various bioactive agents in cranberries and Manuka honey against dental caries bacteria Streptococcus mutans and thus explore their potential as an alternative to traditional oral health care. METHODS: Different cranberry extracts, Manuka honey and methylglyoxal were subjected to an agar well-diffusion assay. By comparing the zones of inhibition around the wells with individual extracts and the extracts in combination, the most synergistic combinations were determined. Serial dilutions of these extracts were then added to a 96-well plate in a so-called checkerboard assay. By finding the minimum inhibitory concentrations (MIC) and the fractional inhibitory concentrations (FIC) contributed by each agent, synergy was determined. RESULTS: Synergy was demonstrated in two of the cranberry extracts tested with methylglyoxal, the bioactive agent in Manuka honey. CONCLUSION: The synergistic combinations found in this research appear to be good candidates for fighting dental plaque and caries.
  • Item
    The effects of aggregated seed arrival and soil heterogeneity on plant diversity
    (Wichita State University, 2019-04-26) Kjaer, Esben; Houseman, Gregory R.
    When attempting to re-establish native plant communities on degraded lands, seeds are sown or planted using "well-mixed" or uniform mixtures. However, such seed mixtures rarely occur in natural plant communities, where most plants occur near conspecifics due to aggregated seed dispersal. Additionally, soil conditions often vary in unknown ways potentially influencing the establishment success of sown plant species. We tested how seed distributions (uniform versus aggregated) and soil heterogeneity influence species richness in plant communities in a grassland in south-central Kansas. We established 96, 4x4.8 m plots each divided into 120 large-scale patches (0.4x0.4 m) or 480 small-scale patches (0.2x0.2 m). We then excavated, mixed, and redistributed soil within each plot to create either homogenous or heterogeneous soil conditions. Seeds were sown with either one species per patch, to create aggregated species distributions within the plot, or were sown uniformly throughout the plot. After two years, we found that species richness did not vary between plots with homogenous or heterogeneous soils and that the responses were similar in plots with large or small patch sizes. However, plots with aggregated seed sowing had higher species richness than plots with uniform sowing. These results suggest that utilizing aggregated rather than uniform seed dispersal may be important to enhance local species richness when restoring prairie ecosystems.
All items in SOAR are protected by copyright, with all rights reserved, unless otherwise indicated.