Genetic and morphological variation analyses of Dryophytes japonicus (Anura, Hylidae) with description of a new species from northeastern Japan.

Japanese tree frog, Dryophytes japonicus, formerly known as Hyla japonica, is known to include several geographic groups recognized in mitochondrial phylogeny. By analyzing genetic and morphological variations in a large number of individuals of Dryophytes, we studied their taxonomic relationships. A mitochondrial DNA phylogeny was consistent with previous studies in that a high molecular divergence existed between populations from northeastern Japan and Sakhalin (Clade A) and those from southwestern Japan and Korea (Clade B). Nuclear DNA analyses based on SNP data also support such separation, whereas hybrid populations were found at some localities near the border of mitochondrial clades in Honshu Island, forming a hybrid zone. The width of hybrid zone was estimated to be narrow (approx. 25 km) and the migration rates into/beyond it were relatively low. Those results indicate that two genetic groups have long been parapatrically maintained with a narrow hybrid zone in Honshu Island. We examined syntypes of Hyla japonica and designated lectotypes. In adult morphology, the clades could be differentiated mainly by the pattern of rear of thigh, and the lectotypes proved to be Clade B. From these results, we describe the frogs of Clade A as a new species, D. leopardus sp. nov., distinct from D. japonicus.