Systematics of Etheostoma camurum and E. chlorobranchium (Osteichthyes: Percidae) in the Tennessee and Cumberland River Drainages with Analysis of Hybridization in the Nolichucky River System

Abstract

The taxonomic relationship of Etheostoma camurum and E. chlorobranchium (Osteichthyes: Percidae) has remained unclear because of their morphological similarity and, prior to this study, the lack of any known area of contact. Taxonomically problematic populations from the Cumberland and Tennessee drainages were analyzed using informative meristic characters and nuptial coloration of males. Data from these analyses indicate that the population in the Hiwassee River is assignable to E. camurum, and populations in the Pigeon River and Abrams Creek are assignable to E. chlorobranchium. During the summer of 1991, an area of the Nolichucky River in Unicoi County, Tennessee, was found that apparently contained both E. chlorobranchium and E. camurum. This contact area contained nuptial males with coloration intermediate between that of either species, putative hybrids, along with nuptial males of each of the parental color types. Limited hybridization in this area is also supported by morphometric and informative meristic data. Allozyme analysis demonstrates more extensive hybridization in the area of contact than do morphometric data but limited introgression of alleles outside of the contact zone. Despite the apparent hybridization that exists in the zone of contact, the gene pools of each species appear to be effectively isolated, and parental phenotypes of both species are found throughout the zone, suggesting that E. camurum and E. chlorobranchium should continue to be regarded as distinct species.