Systematics of Etheostoma camurum and E. chlorobranchium (Osteichthyes: Percidae) in the Tennessee and Cumberland River drainages

The taxonomic relationship of Etheostoma camurum and E. chlorobranchium (Osteichthyes: Percidae) has remained unclear due to their morphological similarity and, before this study, the lack of any known area of contact. During the summer of 1991, an area of the Nolichucky River near Erwin, Unicoi Co., TN, was found that apparently contained both E. chlorobranchium and E. camurum. An analysis of nuptial male coloration in this area revealed the presence of a few individuals with coloration intermediate between that of either species, apparently hybrids, along with individuals of each of the parental color types. Selected meristic data are presented in this study from specimens from the Nolichucky River system and other river systems in the Tennessee and Cumberland drainages. These data, like the color data, suggest a limited amount of hybridization between these species in the area of contact. Allozyme analysis indicates a high level of hybridization in the area of contact in the Nolichucky, but essentially no introgression of alleles outside of this contact zone. Despite the level of hybridization that exists in the zone of contact, the gene pools are effectively isolated, and each species seems to be maintaining its own identity and cohesion. In addition, the identity of problematic populations is discussed for these species within the Tennessee and Cumberland drainages. This evaluation assigns the Hiwassee River, lower Little Pigeon River, and the North Fork of the Holston River populations as E. camurum, and assigns the Pigeon River and Abrams Creek populations as E. chlorobranchium.