Isaac Gibson

Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Forest Resource Management

Committee Chair

Amy B Welsh

Committee Co-Chair

Daniel A Cincotta

Committee Member

Stuart A Welsh


Candy Darters Etheostoma osburni and Variegate Darters E. variatum are both native to streams of West Virginia and Virginia. The geographic ranges of these two species were historically separated by Kanawha Falls, a natural barrier to fish dispersal located at Glen Ferris, WV. Habitat degradation may have reduced the geographic range of Candy Darters, a species of concern in West Virginia and Virginia as well as a federal species of concern. Currently, the species is undergoing a review for listing under the U.S. Endangered Species Act. In the early 1980s, Variegate Darters or putative hybrids were first collected at locations upstream of Kanawha Falls, and have since undergone range expansion. Genetic and morphologic data were examined for individuals from the New, Gauley, and Greenbrier river drainages. Individuals were genotyped using a suite of 5 microsatellite loci to investigate potential hybridization. There was strong evidence for the existence of Distinct Population Segments (DPS) of the Candy Darter. Widespread hybridization, however, was found throughout populations of the Candy Darter. A geographic hybrid zone was estimated with the highest levels of introgression representing the kernel of the hybrid swarm and the locations of F1 hybrids delineating the periphery. The F1 hybrid was meristically evaluated as intermediate within and across characters for parental species. Introgressive hybridization threatens the genetic integrity of the Candy Darter, and may lead to population extirpation and/or extinction.