BIOCHEMICAL PHYLOGENETICS AND HISTORICAL BIOGEOGRAPHY OF HYNOBIUS BOULENGERI AND H. STEJNEGERI (AMPHIBIA: CAUDATA) FROM THE KYUSHU REGION, JAPAN

Wide Distribution but Low Differentiation: Phylogenetic Relationships and Phylogeography of Hynobius nigrescens (Amphibia: Caudata)

We surveyed the genetic structure of Hynobius nigrescens Stejneger, 1907, a lentic breeding salamander widespread throughout montane and lowland regions of northeastern Japan. We performed a mitochondrial DNA analysis to explore intraspecific genetic variation and infer the evolutionary population history of H. nigrescens. Complete 1141 bp sequences of the mitochondrial cytochrome b gene were studied for 134 adult and larval individuals collected from 62 localities, encompassing the known range of the species. Hynobius nigrescens proved to be monophyletic, including two major clades (Clade II from southwestern Hokuriku and Clade I from all other localities). The latter clade comprises four well-supported and geographically structured subclades, which show genetic distances smaller than those seen in the widely sympatric species Hynobius lichenatus. Results of population statistical analyses indicated that Clade II of the westernmost range of H. nigrescens seems to have maintained a constant population size, while Clade I from most of the northeastern species range shows a tendency of recent population expansion, which is evident in Subclades I-A from the northernmost range and I-B from southern Tohoku to northern Kanto and eastern Chubu. In contrast, Subclades I-C from northeastern Chubu and Sado Is. and I-D from northwestern Chubu to Hokuriku seem to have been relatively stable in population size. Hynobius nigrescens differs greatly from other salamander species from northeastern Japan in its much more recent periods of genetic differentiation and its pattern thereof, and is suggested to be a young faunal element in this region.

Taxonomic Relationships of Hynobius stejnegeri and H. yatsui, with Description of the Amber-Colored Salamander from Kyushu, Japan (Amphibia: Caudata)

Examination of the holotype of Hynobius stejnegeri Dunn, 1923 revealed that the species is identical with H. yatsui Oyama, 1947 , recently resurrected from H. naevius (Temminck and Schlegel, 1838). The name H. yatsui is therefore relegated to a subjective junior synonym of H. stejnegeri. The latter name, however, has been widely applied to an amber-colored or tortoise-shell salamander from Kyushu, southwestern Japan, which now requires a new name. We, thus, describe the ambercolored salamander as a new species Hynobius ikioi. The new species is phylogenetically very close to H. amakusaensis Nishikawa and Matsui, 2014 and H. osumiensis Nishikawa and Matsui, 2014 , both also from Kyushu, but is easily distinguished from them by its uniquely bi-colored dorsum.

Morphological and Allozymic Variation in Hynobius boulengeri and H. stejnegeri (Amphibia: Urodela: Hynobiidae)

We studied morphological and allozymic variation in populations of Japanese salamanders, Hynobius boulengeri and H. stejnegeri. Adult H. boulengeri showed sexual dimorphism, and juveniles differed greatly from adults in many morphological characters. From the results of multivariate analyses of morphological characters, the populations were divided into four groups: (I) H. boulengeri from Honshu, (II) H. boulengeri from Shikoku, (III) H. boulengeri from the Sobo-Katamuki Mountains of Kyushu and H. stejnegeri, and (IV) H. boulengeri from the Amakusa Islands and the Osumi Peninsula. Phenotypic relationships among the four groups were identical to relationships clarified by allozymic analyses, except for group IV, which was included in group III in the allozyme tree. Some morphometric characters were significantly correlated with environmental variables. We consider H. stejnegeri to be a valid species based on its unique color pattern, morphometric characters, and allelic composition, even though it was nested within group III of H. boulengeri by both morphological and allozymic analyses. We propose that group I from Honshu and group II from Shikoku should be treated as H. boulengeri sensu stricto and H. hirosei, respectively. Resolving the taxonomic status of the remaining populations of groups III and IV from Kyushu requires further study.