Phylogenetic relationships of Hynobius naevius (Amphibia: Caudata) as revealed by mitochondrial 12S and 16S rRNA genes

Using mitochondrial 12S and 16S rRNA sequences, we investigated phylogenetic relationships among populations of the endemic Japanese salamander Hynobius naevius. Monophyly of this species was recovered only in the maximum parsimony tree and was unresolved in maximum likelihood and Bayesian trees. Instead the following four haplotype clades consistently emerged clearly: Clade 1 from northwestern Kyushu, Clade 2 from Chugoku and northeastern Kyushu, Clade 3 from western Shikoku and Kyushu, and Clade 4 from Chubu-Kinki and central-eastern Shikoku. Of these, Clades 1 and 2, and Clades 3 and 4, respectively, correspond to Groups A and B previously recognized from the analyses of allozyme data in this species, but monophyly of these groups was not strongly supported. Unlike the previous results, the western and eastern samples from Shikoku did not form a clade, and were grouped with Kyushu-B in Clade 3 and Chubu-Kinki in Clade 4, respectively. The reason for this conflict between mtDNA and allozyme results is unknown, but might be related to retention of ancestral mtDNA polymorphism in Shikoku populations. Nearly simultaneous divergence of as many as four lineages in wide-ranging H. naevius is inferred for the late Miocene-Pliocene history of this taxon.