Biodiversity of Cave-Obligate Animals on the Domain of the University of the South, Franklin County, Tennessee

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Dixon, Groves
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Department of Biology, University of the South , Sewanee, Tennessee , Cave-obligate , Haplotype , Biodiversity , Gene flow , Cytochrome c oxidase , Troglobite , Stygobite
The southern Cumberland Plateau in Tennessee and Alabama has the greatest diversity of cave obligate animals in the United States. The 13,000 acre campus (referred to as the ‘Domain’) of Sewanee: The University of the South is located on the southern Cumberland Plateau in Franklin County, Tennessee. There are more than 70 caves on the Domain, which, combined, have more than 15 km of horizontal passageway. We examined the biodiversity of cave animals on the Domain at the species level and at the genetic level. Through a survey of the seven largest horizontal caves on the Domain, we identified 21 cave-obligate species, including two new county records. This accounts for nearly half of the species reported for Franklin County. For our genetic analysis, we selected five diverse taxa (a millipede, a beetle, a fly, an aquatic isopod, and a spider) that were collected from multiple caves, and compared their mitochondrial cytochrome oxidase I gene sequences. Across the five taxa we found: (1) low genetic diversity within caves (mean nucleotide diversity within caves across all taxa: 0.25%), (2) high genetic divergence between caves (divergence between caves within taxa ranged from 2.5%-10.9%, with two exceptions), and (3) little evidence for gene flow between caves (FST between caves within taxa > 0.57, with one exception). Thus, the Domain supports tremendous species diversity, and an even more remarkable level of genetic diversity within those species across caves on a very small scale (no caves used in the genetic comparisons were >3 km apart). Our observation of high genetic divergence between caves on a small scale highlights the importance of cave conservation on a regional scale.