Evolutionary Divergence in the Genus Taricha (Salamandridae)

Abstract

Genetic variation at 18 loci which code for enzymes and proteins has been assessed by means of starch gel electrophoresis in the species and subspecies of the genus Taricha. The average proportion of polymorphic loci per population ranges from 20.4% in T. t. torosa to 41.2% in T. granulosa while the proportion of loci at which an individual is heterozygous ranges from 5.3% in T. t. torosa to 10.9% in T. rivularis. Genetic similarity (I) and genetic distance (D) statistics were computed from allelic frequencies. The mean I and D values between consubspecific populations are 0.972 ? 0.009 and 0.029 ? 0.010, respectively. A southern population of T. t. torosa has a D value of 0.109 when compared to northern populations of T. t. torosa; such genetic divergence is comparable to that found between T. t. sierrae and the northern populations of T. t. torosa (D = 0.126). This supports preexisting evidence of divergence between the northern and southern populations of T. t. torosa and suggests that this species may consist of three subspecies. The mean I and D between the species are 0.633 ? 0.013 and 0.466 ? 0.021, respectively. The amount of genetic divergence we have found between these taxa is remarkably similar to estimates in man, mice and Drosophila. Our results, however, indicate greater genetic divergence within the genus Taricha than was previously suspected.