MTDNA GENE SEQUENCE, ALLOZYME, AND MORPHOLOGICAL UNIFORMITY AMONG REDDIAMOND RATTLESNAKES, CROTALUS-RUBER AND CROTALUS-EXSUL

Genetic and morphological diversity were investigated in two species o f red diamond rattlesnakes. Crotalus exsul Garman, 1884 occurs on Isla de Cedros, and Crotalus ruber Cope, 1892 is found on the peninsula of Baja California, in southern California, and on many islands in the G ulf of California. A partial sequence consisting of 297 nucleotide bas e pairs from cytochrome b of the mitochondrial DNA genome revealed a s ingle difference only, a level of variation common between rattlesnake subspecies. A phylogenetic analysis showed C. exsul to possess the de rived state. The products of 29 gene loci were resolved using horizont al starch gel electrophoresis, No fixed differences were observed to o ccur, although gene frequencies at one locus, catalase-A, were signifi cantly different (P < 0.00004). Among the 16 morphological characters gathered, none served to unequivocally identify the two taxa. The resu lts of a principal components analysis, using eight morphological char acters, revealed that the characters of the Isla de Cedros specimens r epresented a small subset found in the peninsular Baja California spec imens. A multivariate discriminate function analysis could correctly i dentify 94% of C. ruber and 83% of C. exsul. Because of the close simi larity among these two taxa, we believe the red diamond rattlesnakes a re best considered a single species, C. exsul, and the peninsular popu lation retained as C. e. ruber; one Gulf of California population is r ecognized as C. e. lorenzoensis.