Honors Theses

Date of Award


Document Type

Undergraduate Thesis



First Advisor

Ryan Garrick

Relational Format



As a major hotspot of biodiversity, the Appalachian Mountains have been a source of great interest for ecologists in many ways. The mountains' north-south orientation, varying degrees of elevation and environmental conditions, and historical cycles of glacial encroachment have been thought to contribute to this unusual level of population variation. As such, population genetic studies of species have been a growing area of investigation. Phylogeography, the study of how historical processes could lead to current geographic distributions of individuals and populations of a species, is a particularly prominent direction. The focus of this study examines the horned passalus and its dispersal in relation to the idea that the Southern Appalachians functioned as a refugium during the Last Glacial Maximum. Two scenarios that are being considered is whether the Southern Appalachians are comprised of one general refugium or the entire region involved several scattered refugia. This will be tested by comparing genetic diversity of different populations of the horned passalus sampled throughout the region and its association to spatial distribution within the region. Step-wise gradients in genetic diversity levels and positive correlations between spatial and genetic distances would be expected from single refugium conditions. Dispersed refugia would be predicted to have scattered pockets of populations with varying levels of genetic diversity rather than a clear gradient and fluctuating genetic distances between populations. The mitochondrial CO1 gene and the nuclear H3A gene were used as markers to generate sequence data through Polymerase Chain Reaction (PCR). The results of this investigation seemed to support the first scenario of a single, large refugium. Greatest genetic diversity was found within the southern part of the Southern Appalachians, and increased spatial distance from populations within this region corresponded with increased genetic distances. However, the H3A gene yielded data that was either contradicting or difficult to interpret. Further analyses and addition of sequence data seem necessary in order to provide greater insight into the population genetics of the horned passalus.

Included in

Biology Commons



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