Redescription and Recognition of Etheostoma cyanorum from Blue River, Oklahoma

Abstract

Etheostoma cyanorum, endemic to the Blue River drainage of southern Oklahoma, is redescribed and recognized as a distinct species within the Etheostoma whipplei–Etheostoma radiosum complex, separating it from E. radiosum. Originally described as Poecilichthys radiosus cyanorum, it was one of three putative subspecies of E. radiosum (with E. r. radiosum and E. r. paludosum) considered valid until now, defined in part by drainage-specific allopatry. Two separate mtDNA gene trees show that E. cyanorum forms a distinct and strongly supported lineage. Ten meristic and 16 morphometric traits are reexamined and new information included, confirming traits separating E. cyanorum from E. radiosum, and clarifying ambiguities about “bluntness of the snout” as diagnostic for P. r. cyanorum. Etheostoma cyanorum differs from E. radiosum by lower counts of unpored lateral line scales, higher counts of pored lateral line scales, and greater interorbital width. Large adult E. cyanorum have a deep body and blunt snout per earlier studies, but those traits are not diagnostic due to allometry. Head depth and head width can separate E. cyanorum from most populations of E. radiosum, but they overlap with some populations of E. radiosum in southwest Arkansas. All evidence supports recognition of E. cyanorum as a valid species. A broad geographic, molecular assessment to supplement existing morphological information is needed to assess validity of the two remaining subspecies of E. radiosum.