Degree Name

Master of Science (MS)

Semester of Degree Completion

2002

Thesis Director

Mark Mort

Abstract

Phylogeography is defined as the spatial distribution of taxa with respect to geologic and geographic events. It is well documented that the distributions of many taxa have been affected by glacial events during the Pleistocene Era. The patterns generated can be very complex and result from shifts in climate and/or vegetation.

The Seal salamander, (Desmognathus monticola), is one species that still has questions pertaining to its phylogeography. The range of this species extends from southwestern Pennsylvania to northern Alabama and Georgia, with a highly disjunct, state-endangered population in the Red Hills of Alabama. The main goal of this study is to determine the origin of this disjunct population through an extensive field survey. In addition, the utility of a relatively new genetic technique will be tested, with possible conservation implication for this population.

Three hypotheses were proposed to explain the origin of the southern population. First, it is possible that this population may not be disjunct, but instead may have a continuous range extending throughout the state of Alabama. If disjunct, then two additional hypotheses could be proposed. The southern population may represent a recent derivative from the main range, or it may be a relictual population formed through historic glacial events in the Appalachian region.

Based upon a review of topographic maps and an extensive field survey of this intervening region, we concluded that D. monticola were not present in this area and that the Red Hills population is truly disjunct. Thus, the first hypothesis could be rejected. To address the final two hypotheses, Intersimple Sequence Repeats were employed, and networks of relatedness were constructed using parsimony and neighbor-joining methods. These data indicate the Red Hills population (10 bands) and the Tubmill population (8 bands), in the northern extreme of the range, harbor the highest numbers of population-specific bands. Remaining populations had three or fewer population-specific bands, and held only a subset of the bands present in the Red Hills and Tubmill populations. The Tubmill population was sister to the remaining populations; wherever, the Red Hills population was nested within each tree generated. To address this situation, constraint analyses were conducted to place the Red Hills as sister to all other populations. The tree generated was the same length of the unconstrained tree (L=570), which indicates that the Red Hills population could be sister to the remainder of the populations sampled.

Our data thus indicate the potential for two refugial populations, possibly isolated during glacial events of the Pleistocene Era. A bi-directional recolonization from the northern and southern extremes may have occurred. The southern population was probably isolated due to shifts in climate and/or vegetation, while the northern population may be a more traditional glacial refugium.

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