MtDNA phylogeography of the California newt, Taricha torosa (Caudata, Salamandridae).

Thirty-six individuals of the California newt, Taricha torosa, representing 22 populations from throughout the range of the two currently recognized subspecies, torosa and sierrae, were examined for sequence variation in a segment (375 bp) of the mitochondrial (mt) cytochrome b gene. The maximum sequence divergence within T. torosa is about 9%. Phylogenetic analyses used the sister taxa T. rivularis and T. granulosa as outgroups. Eighteen haploid sequence types found in T. torosa were grouped by parsimony, maximum likelihood, and neighbor-joining analyses into five mitochondrial clusters: two in torosa (the northern and southern clusters) and three in sierrae (the northern, central, and southern clusters). The southern sierrae cluster apparently shared a most recent common ancestor with the northern torosa cluster. The approximate time of sequence divergence within the current species was calibrated using the known fossil record (0.8% divergence per million years or 0.01 maximum likelihood distance per million years). Phylogenetic implications of mtDNA sequence variation for evolution and biogeography of the T. torosa species complex are discussed.