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| Hynobius oni Kanamori, Nishikawa, Matsui & Tanabe, 2022 DOI: 10.7717/peerj.13891 |
Abstract
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.
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| Live male topotype of Hynobius hirosei (KUHE 62827; A–C) and male holotype of Hynobius oni (KUHE 62785; D–F). (A, D) Dorsal views. (B, E) Lateral views. (C, F) Ventral views. Scale bar shows 20 mm. |
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| Figure 5: Live individual (KUHE 61096) of Hynobius oni. |
Hynobius oni sp. nov.
(Japanese name: Nan-yo-sanshouo)
Diagnosis: A large-sized species (adult SVL 73.6–87.5 mm in males) of the lotic-breeding Hynobius, breeding in montane streams; dorsum uniformly dark reddish brown and immaculate in adult; tips of fore- and hindlimbs adpressed on body scarcely meeting (overlap of −2.0 to 0.0 costal folds in males); fifth toe well developed; ova large, pigmentless; egg sacs relatively long and crescent in shape, with distinct whiptail structure on free end; larvae lack claws on their tips of fingers and toes; most similar to H. hirosei, but distinct based on its smaller body size, longer axilla-groin distance, shorter tail length, shorter internarial distance, longer upper eyelid length, and larger medial tail width. Hynobius oni is genetically closer to H. sematonotos than H. hirosei based on mtDNA; however, H. oni has no large markings on the body, in contrast to many silvery spots on H. sematonotos, and a larger SVL than H. sematonotos.
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| Habitat of Hynobius oni in the type locality. |
Etymology: The specific name is derived from the “Oni” in Japanese, which is a traditional Japanese demon. The habitats of the new species are areas where prior generations believed that the Oni and Ushi-oni, which is a type of Oni, occurred. The type locality is located in the Oni-ga-jo Mountains, which is considered to be the castle of the Oni.
Conclusions:
In the present study, the actual genetic population structure and degree of genetic divergence within Hynobius hirosei, which has been reported to have large genetic intraspecies divergence, were evaluated using mtDNA and nuDNA markers (SNP). Phylogenetic analysis using mtDNA revealed three divergent lineages, including the Tsurugi, Central, and Nanyo groups (genetic distance: 6.9–10.3% in cyt b). Further, STRUCTURE analysis using SNP revealed that the Nanyo group is genetically isolated from the other groups and the Tsurugi and Central groups form hybrid zones. Morphological analyses also revealed that the Nanyo is distinct from the other groups. Collectively, these results strongly indicate that Nanyo group is a distinct species, and is referred to as H. oni sp. nov. in this study.
Sally Kanamori, Kanto Nishikawa, Masafumi Matsui and Shingo Tanabe. 2022. A New Species of Lotic Breeding Salamander (Amphibia, Caudata, Hynobiidae) from Shikoku, Japan. PeerJ. 10:e13891. DOI: 10.7717/peerj.13891
