Speciation with Little Genic and Morphological Differentiation in the Ribbon Snakes Thamnophis proximus and T. sauritus (Colubridae)

Coefficients of genetic similarity based on electrophoretic data on proteins of Thamnophis proximus and T. sauritus were within the range usually observed for conspecific populations. Levels of polymorphism and heterozygosity were not unusually low; rather, the high genetic similarity between the species reflected similarity of allelic frequencies at the polymorphic loci. Discriminant functions analysis of quantitative morphological characters also differentiated the species only weakly. Ecological differences and superficial morphological differences, however, indicate that they are valid biological species.