Genetic Variation in Western Members of the Macrhybopsis aestivalis Complex (Teleostei: Cyprinidae), with Emphasis on Those of the Red and Arkansas River Basins
We used protein electrophoresis of the allozyme products of 21 gene loci to examine relationships among five western species of the Macrhybopsis aestivalis complex (sensu Eisenhour, 1997), with emphasis on three species recognized from morphology in the Red and Arkansas river basins. Monophyly was supported for both species endemic to those basins, M. australis in the Red and M. tetranema, in the Arkansas. However, support was weak because of high genetic similarity between these species and the more wide-ranging species, M. hyostoma. Within the Arkansas and Red river basins, only 2% and 5%, respectively, of total genic diversity was attributable to differences between the endemic species and M. hyostoma. Across all samples from the two basins, only 14% of total diversity was attributable to among species differences. Phenetic and allele-frequency parsimony analyses grouped M. hyostoma from the Red and Arkansas river basins with the associated endemic in the respective basin rather than with populations of M. hyostoma from elsewhere. The results are consistent with the indication from morphology that M. tetranema and M. australis are sister species, if it is assumed that the present patterns of allozyme variation are a result of subsequent contact and introgressive hybridization with M. hyostoma. Collections of M. aestivalis from the Rio Grande Basin and M. marconis from the San Marcos River Basin were markedly divergent from each other and from other members of the complex.
Copeia, Vol. 2003, No. 3, 493-501.