Taxonomic Reassessment of the Izumo Lineage of Hynobius utsunomiyaorum: Description of a New Species from Chugoku, Japan

Taxonomic reassessment of salamanders (genus Hynobius) from Tsushima Islands, Japan, with a resurrection of Hynobius tagoi Dunn, 1923 (Amphibia: Caudata)

To clarify the taxonomic status of salamanders from Tsushima Islands, Japan, we examined two species of salamanders, Hynobius tsuensis and Hynobius sp. from Tsushima Islands, and compared them with H. nebulosus from Kyushu. We found that the three taxa differ from each other in nuclear DNA, adult morphology, and egg-sac shape, and consider them to be independent species. Based on the investigation of type specimens of the synonyms, we identified Hynobius sp. as H. tagoi Dunn, 1923 and redescribe it herein. Also, we designate a neotype for H. tsuensis and redescribe H. tsuensis. The distribution areas of the two species partly overlap but they were distinguishable by their body colorations: H. tsuensis has uniformly blackish tail sides and a distinct yellow stripe on the upper tail edge; whereas H. tagoi has brown tail sides with numerous dark stippling and without a distinct yellow stripe on the upper tail edge.

Reassessment of species delimitation using nuclear markers in three lentic-breeding salamanders from the Chugoku District of Japan (Amphibia: Caudata: Hynobiidae)

Hynobius akiensis sensu lato has recently been split into three species based on short sequence analyses of cyt-b gene of mtDNA and without data of nuclear DNA, and strange sympatric distribution in some areas has been indicated in two species. We analyzed nuclear DNA marker (SNPs) and complete sequence of cyt-b in H. akiensis sensu lato to reassess species delimitation and genetic introgression among species. As a result, we found two lineages with discordant mitochondrial and nuclear DNA in some areas. Of H. akiensis sensu lato, each of the two contains the type locality of two species recently reported (H. sumidai and H. geiyoensis), and the use of these names has been previously advocated. However, their sympatric distribution was rejected based on nuclear DNA data, which we consider is more reliable than mtDNA. We thus clarify geographic boundary of these two species and revise the species delimitations.

A new species of lotic breeding salamander (Amphibia, Caudata, Hynobiidae) from Shikoku, Japan

Background

Hynobius hirosei is a lotic-breeding salamander endemic to Shikoku Island in western Japan. Significant allozymic and morphological differences have been found among the populations of this species; however, the degree and pattern of intraspecific variation have not been surveyed using a sufficient number of samples.

Methods

For the taxonomic revision of H. hirosei, we conducted genetic and morphological surveys using samples collected throughout the distribution. Phylogenetic analysis using the cytochrome b region of mitochondrial DNA and population structure analysis using single nucleotide polymorphisms were conducted to evaluate the population structure within the species and the degree of genetic differentiation. Subsequently, a morphological survey based on multivariate and univariate analyses was performed to assess the morphological variation.

Results

Genetic analyses revealed three genetic groups (Tsurugi, Central, and Nanyo) within H. hirosei, with the Nanyo group distributed allopatrically from the others, and the Tsurugi and Central groups distributed parapatrically with the formation of a hybrid zone between them. The Nanyo group was morphologically distinguishable from the remaining samples, including the topotype of H. hirosei, based on a smaller body size and several ratio values of characters to snout-vent length, longer axilla-groin distance, shorter tail length, shorter internarial distance, longer upper eyelid length, and larger medial tail width. These results support the notion that the Nanyo group is an undescribed species. However, the remaining genetically differentiated groups could not be divided in the present study. Herein, we described the Nanyo group as a new species.