Introgressive Hybridization of Smallmouth Bass (Micropterus dolomieui) and Guadalupe Bass (M. treculi)

The introduction of smallmouth bass (Micropterus dolomieui) into the range of the endemic Guadalupe bass (M. treculi) on the Edwards Plateau in southcentral Texas has resulted in hybridization between these species. Sympatric populations of smallmouth bass and Guadalupe bass from two discrete locations on the Edwards Plateau were analyzed on the basis of biochemical genetics and meristics. Electrophoretic and meristic evidence revealed no interspecific hybrids in Lake Travis. It appears that smallmouth bass have not adapted well in this lake, perhaps contributing to the lack of genetic exchange with Guadalupe bass. In contrast, the Canyon Lake populations are actively interbreeding, and diagnostic allozyme loci clearly revealed genetic introgression between these two species. Genetic analysis proved to be a more sensitive tool for detecting F2 or backcross individuals than the meristic index. The genetic integrity of Guadalupe bass appears to be seriously threatened in at least part of its highly restricted range.