Biochemical Evidence for Congeneric Competition as a Factor Restricting Gene Flow Between Populations of a Darter (Percidae: Etheostoma)

Abstract

Echelle, A. A., A. F. Echelle, and B. A. Taber (Biology Department, Baylor University, Waco, Tx. 76703 and Biology Department, Southwest Missouri State University, Springfield, Mo.) 1976. Biochemical evidence for congeneric competition as a factor restricting gene flow between populations of a darter (Percidae: Etheostoma,). Syst. Zool. 25:228–235.—Electrophoretic analysis of proteins encoded by polymorphic loci demonstrates that Etheo-stoma spectabile populations show greater differentiation in allelic frequencies in an area of sympatry with E. radiosum than in an area of allopatry. The data are more compatible with the assumption that degree of gene-flow rather than natural selection is the primary mechanism maintaining local differentiation. Increased heterogeneity in sympatry is attributed to exclusion of spectabile from downstream areas through competition with radio-sum, thereby isolating spectabile in headwater areas and restricting gene flow between populations. In sympatry, spectabile showed greater differentiation than radiosum, presumably because of greater gene flow in the latter.