| dc.description.abstract | A recent study recognized two distinct morphological types of speckled chub (cf Macrhybopsis aestivalis) in the Arkansas River drainage. The purpose of this study was to use protein electrophoresis to examine taxonomic status and genetic relationships of the two forms. A total of 196 speckled chub were conected from eight sites in Kansas and Oklahoma, seven in the Arkansas River drainage and one in the Wabash River in Indiana. The samples were assayed for genetic variation at 24 protein-encoding gene loci. The data were analyzed for insight into population structure. Phylogenetic relationships were examined on the basis of allele frequency parsimony and the distance-Wagner procedure. The results, together with other studies, support recognition of two species in the Arkansas River drainage, M. tetranema, which is endemic to the drainage, and the more widespread M. hyostoma, which occurs elsewhere in the Mississippi River basin. The endemic species probably arose in the Ancestral Plains Stream, which drained much of western Kansas and Oklahoma and emptied into the Gulf of Mexico independently of the Mississippi River. Headward erosion of the Ancestral Arkansas River in the Pleistocene would have captured a portion of the Ancestral Plains Stream, bringing M. tetranema into contact withM hyostoma. The genetic results, together with morphology, suggest that M hyostoma in the Arkansas River drainage are intergrades with M tetranema. The latter species, which has disappeared over approximately 90% of its geographic range, now consists of two widely disjunct, geographically restricted populations. Aspects of genetic structure are discussed with respect to management implications for this declining species. | |
