Phylogenetic relationships of two Salamandrella species as revealed by mitochondrial DNA and allozyme variation (Amphibia: Caudata: Hynobiidae)

We conducted molecular phylogenetic analyses to confirm taxonomic relationships and to delimit distributional ranges of Siberian salamanders, Salamandrella keyserlingii and Salamandrella schrenckii, and to elucidate the origin of the isolated population of this species complex on Hokkaido, Japan. Phylogenetic trees constructed by MP, NJ, ML, and Bayesian methods, using complete sequences of mitochondrial cytochrome b genes, all indicated monophyly of Salamandrella and of each of the two species. Identical relationships were found on UPGMA, NJ, and CONTML trees derived from electrophoretic analysis of variation in 18 inferred allozyme loci. Populations from Hokkaido and northeastern China proved to be S. keyserlingii, while populations from Khabarovsk and Lazovsky are S. schrenckii. Genetic differentiations of S. keyserlingii within Sakhalin, and between Sakhalin and Hokkaido, are substantial. The Hokkaido population is hypothesized to have been isolated on the island since early Pleistocene, much earlier than isolation of sympatric anuran populations from their Sakhalin relatives. In contrast, the continental populations of S. keyserlingii are only slightly differentiated from some Sakhalin populations, and are thought to have expanded their ranges in the late Pleistocene.