Caecidotea holsingeri and the epikarst

The distribution pattern of troglobites is affected by their cave invasion route. The goal of this project was to examine the role of the epikarst as being the primary habitat of one troglobitic aquatic isopod species located in Greenbrier County, West Virginia, Caecidotea holsingeri, in which case the isopods would passively colonize cave passages by "raining down" from the epikarst. The hypothesis was tested by comparing the genetic relatedness among C. holsingeri and Gammarus minus populations collected from several streams in the Organ Cave drainage. The amphipod G. minus migrates upstream, and thus was used as a control. In order for the hypothesis to be tenable, one would have expected greater genetic similarity among C. holsingeri populations than among G. minus populations. The results indicated more genetic relatedness among G. minus than among C. holsingeri. However, several assumptions were included in the hypothesis, and hence the results were inconclusive. In fact, they showed interesting patterns, such as a probable low invasion rate of C. holsingeri between different streams.