Use of mtDNA to Identify Genetic Introgression among Related Species of Catfish

Brown bullheads (Ameiurus nebulosus) are known to hybridize naturally with closely related black (Ameiurus melas) and yellow bullhead (Ameiurus natalis) species. The presence of hybrid specimens may obscure accurate ecological and toxicological studies, which may in turn influence evaluations of aquatic ecosystem health. Thus, there is a need for a reliable method to detect introgression in bullheads from tissue samples collected in the field. Specimens from each bullhead species were identified using taxonomic keys and descriptions of morphological characteristics. The morphological identifications were compared with molecular characters from a 431 bp of mtDNA control region sequences. The results identified a single possible A. melas × A. nebulosus hybrid individual out of 11 fish identified as having A. nebulosus morphology from Presque Isle Bay, Erie, PA. Four additional fish revealed possible gene introgression from A. melas to A. nebulosus. We suggest that future studies making toxicological and ecological comparisons examine possible introgression within the bioindicator population.