Cytochrome b phylogeny does not match subspecific classification in the western terrestrial garter snake, Thamnophis elegans

We sequenced a 307-bp fragment of the mitochondrial cytochrome b gene from 42 individuals representing 14 populations of the western terrestrial garte r snake, Thamnophis elegans. Current taxonomy recognizes either five or six subspecies of T. elegans based on color and scale morphology, but all agre e on three major geographic races (T. e. elegans, terrestris, and vagrans). Although the cytochrome b phylogeny did not match subspecific classificati on of the populations, it did yield geographically proximate groups. Popula tions from the Sierra Nevada range and Monterey, California, formed one mon ophyletic group of T. e. elegans and T. e, terrestris, This Sierran/Montere y group was included in a larger group with eastern populations from the Gr eat Basin (T, e. vagrans). The other well-supported group was comprised of populations from the western Great Basin (T. e. vagrans), One population fr om the northern California coast (T. e, terrestris) was basal to both group s of populations. Thus, neither T. e. vagrans nor T. e. terrestris formed m onophyletic groups. Average percent sequence divergence between the outgrou p (T. sirtalis) and T. elegans was 7.9-12%. Within T. elegans, divergence a mong populations ranged from 0.3-7.7%.