Variation in the Hispaniolan Colubrid Snake Uromacer frenatus Gunther (Reptilia, Serpentes, Colubridae)

Abstract

Variation in the Hispaniolan colubrid snake Uromacer frenatus is discussed throughout its range, including the satellite islands of lie Grande Cayemite, lle-a-Vache and Isla Beata. Details of coloration and pattern are given, and sexual dimorphism in two characteristics is shown. Specimens from the Dominican Peninsula de Barahona differ from their relatives (U. f. wetmorei) on adjacent Isla Beata in color and presumably scutellation, and the peninsular population is named as a new subspecies. * * * The colubrid snake genus Uromacer Dumeril and Bibron is endemic to the West Indian island of Hispaniola. Cochran (1941) recognized six species in the genus; these may be conveniently divided into those which are short-snouted (catesbyi Schlegel, scandax Dunn) and those which are long-snouted (frenatus Gunther, wetmorei Cochran, dorsalis Dunn, and oxyrhynchus Dumeril and Bibron). In the short-snouted taxa, the snout is twice as long as the eye, whereas in the long-snouted taxa, the snout is 2.5 to 3 times as long as the eye. Schwartz (1970) reviewed the variation in the short-snouted group and regarded scandax as a subspecies of U. catesbyi and as well named other subspecies of U. catesbyi. The entire genus was reviewed by Horn (1969); he examined 102 specimens of U. frenatus, including 39 snakes in the Albert Schwartz Field Series (ASFS). His emphasis, however, was not systematic; rather, his approach was evolutionary. Since members of the genus Uromacer are polychromatic (in that members of the same population may be quite differently colored), Horn was interested in explaining this polychromatism and in showing evolutionary patterns in dietary differences between the species. He did reach some systematic conclusions; he considered oxyrhynchus and dorsalis separate species, and frenatus as distinct from the former pair but with a subspecies (wetmorei) restricted to Isla Beata and the Peninsula de Barahona in the southwestern Republica Dominicana. The present paper deals with variation in U. frenatus and the status of U. f. wetmorei. To understand the basic problems involved within the long-snouted Uromacer, a few facts