Sewanee Senior Theses 2007


Recent Submissions

Now showing 1 - 4 of 4
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    Evolution in the dark: A study of cave crickets in Southern Appalachia
    (2007-05-02) Harrison, Mary
    In 1978 Hubbell and Norton described nine species of crickets in the Tribe Hadenoecini found in caves or forest litter in the Southern Appalachians. According to the model proposed by these authors new species formed during glaciation. Hubbell and Norton (1978) suggested that the crickets are thermophile relicts that dispersed in the area before and after glaciation but, during glaciation, formed new species in allopatric refugia of caves or forests south of their normal ranges. Our mitochondrial DNA sequence data—the first obtained for members of this group--tested several hypotheses: 1) The Tribe Hadenoecini is a monophyletic clade when compared with outgroups from their sister Tribe Dolocopodini, 2) The two genera Euhadenoecus and Hadenoecus are both monophyletic, 3) The forest Euhadenoecus and the trogloxenic Euhadenoecus are each monophyletic, 4) The two trogloxenes from Kentucky form a single clade, and the three most cave-adapted trogloxenes in Tennessee form a single clade. Our preliminary results support all four of these hypotheses. Our data, however, suggest that the divergence between the two genera and between the two clades of Hadenoecus occurred well before the Pleistocene and that only speciation within the two Hadenoecus clades occurred in the mid to late Pleistocene as suggested by Hubbell and Norton (1978).
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    Probing the Changes of Microbial Diversity with Land Use Changes on the Cumberland Plateau
    (2007-05-02) Huynh, Thy
    Although there has been a great deal of interest in cataloging and studying the biodiversity of life on the planet, bacterial biodiversity has largely been underestimated until recently because over 99% of all bacteria cannot be cultured. Hence, they could not be identified until scientists learned to identify and classify bacteria by sequencing bacterial 16S rDNA, the gene that encodes the 16S rRNA of the ribosome. Three protocols were adapted to break bacteria cells and release their DNA: Two freeze-thaw methods using either lysozyme or sodium dodecyl sulfate (SDS) did not yield repeatable results, whereas bead-beating produced the most consistent results. The efficiencies of bead-beating with FastPrep Instrument and the SPEX 8000 Mixer Mill to break soil bacterial cells were compared during the beating method; the extraction of bacterial DNA with the Mixer Mill was more effective at breaking soil bacterial cells. Universal and Pseudomonas spp. specific primers were used to amplify 16S rDNA from soil bacteria in polymerase chain reaction (PCR) after isolating DNA by bead beating. Comparison of DNA bands following gel electrophoresis demonstrated that universal bacterial DNA was amplified by PCR from all the different seasonal samples studied at the Cross Creek and Smith Tract, while Pseudomonas sp. DNA was amplified mostly in Smith Tract soil samples.
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    Effect of an Introduced Ambrosia Beetle (Xyleborus glabratus) on Red Bay (Persea borbonia) Mortality in Maritime Forest Communities of St. Catherine's Island, GA
    (2007-05-02) Hess, Matthew
    Over the past three years, red bay (Persea borbonia, Lauraceae) populations along the Georgia coast have experienced high levels of mortality due to an introduced fungal pathogen (Ophiostoma sp.) being spread by outbreaks of a recently introduced, Asian ambrosia beetle, Xyleborus glabratus. The beetle carrying the fungus was believed to have arrived in this country on shipping pallets and was first identified in the port of Savannah, Georgia in 2002. Red bay is an abundant and ecologically important tree species found in the coastal plain of the southeastern United States. This study represents the first assessment of red bay decline, which as a casualty of an introduced pathogen, may be following the same fate as American chestnut, American elm and flowering dogwood in the forests of the eastern U.S. Five 5000m2 plots were established on St. Catherine’s Island, a barrier island south of Savannah. The status of red bay populations in these plots was assessed in 2004, 2005 and 2006 for leaf wilt, diameter at breast height (DBH), and the presence of basal sprouts. It was determined from that red bay is a common species represented in many size classes. Across the five study sites, the proportion of fully wilted red bays increased from 0.06 in 2004 to 0.89 in 2006. A fitted logistic regression model for binary response variables suggested that DBH was not a significant predictor of probability of infection (p>0.05), while site and year were significant (p<0.05). The odds of basal sprouting on a dead tree in 2006 were 7.09 times higher than the odds of sprouting on a live tree. However, potential regeneration by basal sprouts was severely limited by deer browse. A comparison with Dutch Elm Disease (DED) and other significant tree losses suggest that red bay will likely meet the same fate. This will have serious consequences for the already degraded maritime forest ecosystem in terms of species composition, structure and function.
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    Habitat Suitability Analysis for Mountain lions (Puma concolor) on the Southern Cumberland Plateau
    (2007-05-02) Moye, Valerie
    Since the 1940’s mountain lions (Puma concolor) have been extirpated from the eastern United States due to exhaustive hunting, habitat loss, and declining prey populations. Recently, however, evidence suggests that existing mountain lion populations are expanding and recolonizing sites where they have been absent for nearly a century. The southern Cumberland Plateau ecoregion of Tennessee and Alabama, part of the historic home ranges for the extirpated Florida panther (Puma concolor coryi) and Eastern Cougar (Puma concolor cougar), contains some of the largest remaining tracts of contiguous native forests in the southeast. We built this habitat suitability model because the southern Cumberland Plateau represents unique potential mountain lion habitat in the southeastern US and because there is a need for landscape level habitat analyses in the eastern US for this species. Using a geographic information system (GIS) we examined landscape and habitat characteristics including road density, land cover type, patch density, and contagion in seven counties in Tennessee and three counties in Alabama to determine the quality and extent of potential mountain lion habitat in the Southern Cumberland Plateau Ecoregion. Based on habitat characteristics for mountain lions in other areas, we identified between 940 km² and 2,240 km² of likely suitable habitat, which could theoretically support a population of 27 to 65 individuals. High suitability habitat predicted by the model also correlates with the locations of unconfirmed mountain lion sightings in the study area.