Atsushi Tominaga

Phylogenetic relationships of Ansonia from Southeast Asia inferred from mitochondrial DNA sequences: Systematic and biogeographic implications (Anura: Bufonidae)

We investigated the phylogenetic relationships and estimated the history of species diversification and biogeography in the bufonid genus Ansonia from Southeast Asia, a unique organism with tadpoles adapted to life in strong currents chiefly in montane regions and also in lowland rainforests. We estimated phylogenetic relationships among 32 named and unnamed taxa using 2461bp sequences of the mitochondrial 12S rRNA, tRNA(val), and 16S rRNA genes with equally-weighted parsimony, maximum likelihood, and Bayesian methods of inference. Monophyletic clades of Southeast Asian members of the genus Ansonia are well-supported, allowing for the interpretation of general biogeographic conclusions. The genus is divided into two major clades. One of these contains two reciprocally monophyletic subclades, one from the Malay Peninsula and Thailand and the other from Borneo. The other major clade primarily consists of Bornean taxa but also includes a monophyletic group of two Philippine species and a single peninsular Malaysian species. We estimated absolute divergence times using Bayesian methods with external calibration points to reconstruct the relative timing of faunal exchange between the major landmasses of Southeast Asia.

Phylogenetic relationships of two Salamandrella species as revealed by mitochondrial DNA and allozyme variation (Amphibia: Caudata: Hynobiidae)

We conducted molecular phylogenetic analyses to confirm taxonomic relationships and to delimit distributional ranges of Siberian salamanders, Salamandrella keyserlingii and Salamandrella schrenckii, and to elucidate the origin of the isolated population of this species complex on Hokkaido, Japan. Phylogenetic trees constructed by MP, NJ, ML, and Bayesian methods, using complete sequences of mitochondrial cytochrome b genes, all indicated monophyly of Salamandrella and of each of the two species. Identical relationships were found on UPGMA, NJ, and CONTML trees derived from electrophoretic analysis of variation in 18 inferred allozyme loci. Populations from Hokkaido and northeastern China proved to be S. keyserlingii, while populations from Khabarovsk and Lazovsky are S. schrenckii. Genetic differentiations of S. keyserlingii within Sakhalin, and between Sakhalin and Hokkaido, are substantial. The Hokkaido population is hypothesized to have been isolated on the island since early Pleistocene, much earlier than isolation of sympatric anuran populations from their Sakhalin relatives. In contrast, the continental populations of S. keyserlingii are only slightly differentiated from some Sakhalin populations, and are thought to have expanded their ranges in the late Pleistocene.

Reduced genetic variation in the Japanese giant salamander, Andrias japonicus (Amphibia: Caudata)

The phylogenetic relationships among 46 samples from 27 populations of the Japanese giant salamander, Andriasjaponicus and its congener, A. davidianus from China was investigated, using 3664 bp sequences of the mitochondrial genes NADH1, NADH3, cyt b and CR, partial NADH6 and intervening genes. In phylogenetic trees constructed by MP, ML, and Bayesian methods, the family Cryptobranchidae and the genus Andrias both form monophyletic groups. Japanese A. japonicus and Chinese A. davidianus are sister taxa and can be regarded as separate species despite a small degree of genetic differentiation. Andriasjaponicus is divided into central and western clades, but the phylogenetic relationships within the latter clade are unresolved. As previously reported from allozyme analyses, A. japonicus exhibits little genetic differentiation, in strong contrast to salamanders of the genus Hynobius with which their distributions overlap. This reduced genetic variability in A. japonicus is attributable to a unique mating system of polygyny, delayed sexual maturity, notable longevity, life in a stable aquatic environment, and gigantism, as well as bottleneck effects following habitat fragmentation and extinction of local populations during Quaternary glaciations. The species is thus susceptible to extinction by potential environmental fluctuations, and requires extensive conservation measures.

Occurrence of Two Types of Hynobius naevius in Northern Kyushu, Japan (Amphibia: Urodela)

Abstract A survey to examine genetic variation among Hynobius naevius from four localities of Fukuoka Pref., northern Kyushu, Japan, resulted in the detection of two, sympatric, genetic types (A and B) that are clearly different in the allelic frequencies of four loci (ACOH-A, ACOH-B, ADH-A, and SOD-A) in each locality. Morphological investigations between the two genetic types also proved that they are clearly discriminated; the type A is about 75 mm in SVL, lacks mottling pattern on bluish purple dorsum, and possesses relatively short vomerine teeth series, while the type B is about 60 mm in SVL, and has light mottling on reddish purple ground color. These results strongly suggest that reproductive isolation occurs between these two types, and that they could be regarded as separate species. Populations from Toyota-cho, western Honshu, and Yabe-machi, central Kyushu, both close to Fukuoka Pref., were very similar to the types A and B, respectively. From these results, we consider that two evolutionary lineages that first evolved allopatrically in western Honshu and southern Kyushu secondarily contacted and became sympatric in the region of northern Kyushu.

Morphological Discrimination of Two Genetic Groups of a Japanese Salamander, Hynobius naevius (Amphibia, Caudata)

Abstract Hynobius naevius, distributed on western Honshu, Shikoku, and Kyushu Islands of Japan, includes two genetically distinct groups (Groups A and B) that have never been delimited morphologically. Using specimens from the entire species range, we investigated the possibility of distinguishing these groups morphologically. Multivariate analyses of morphometric characters resulted in recognition of two groups that corresponded well to the two genetic groups. One (Group A) was characterized by larger body, compressed tail, shallower vomerine tooth series, bluish- or reddish-purple ground color, and pale-white lateral markings. In contrast, another (Group B) was characterized by smaller body, cylindrical tail, longer vomerine tooth series, reddish-brown ground color, and white lateral markings. Group A was composed of populations from the Chugoku District of Honshu and northern Kyushu, and could not be divided into subgroups, while Group B encompassed populations from the Chubu and Kinki Districts of Honshu, Shikoku and Kyushu, and was subdivided into three local subgroups that are geographically separated by marine straits. Morphometric differentiation in Group A is presumed to have been less affected by genetic factors than by other factors, such as ecological relationships with other, coexisting species. Differentiation in Group B is assumed to have been enhanced not only by genetic but also by climatological factors.

Taxonomic status of a salamander species allied to Hynobius naevius and a reevaluation of Hynobius naevius yatsui Oyama, 1947 (Amphibia, Caudata)

Abstract A Japanese small salamander, Hynobius naevius (Temminck and Schlegel, 1838), has recently proven to include two species (larger [A] and smaller [B]) that are reproductively isolated and are genetically and morphologically distinct from each other. Of these two species, Species A is considered to correspond to true H. naevius. To determine the name of Species B, we investigated five specimens stored at Kyushu University and concluded from the locality and date of collection that they represent syntypes of H. n. yatsui Oyama, 1947. Results of morphological comparisons indicated that the syntypes are identical with Species B. Because this species is distinct from Hynobius naevius at the species level, subspecies H. n. yatsui is elevated to full species rank as H. yatsui. To avoid taxonomic confusion, we designated one male among the syntypes as the lectotype and redescribed the species.

Phylogeography of Hynobius yatsui (Amphibia: Caudata) in Kyushu, Japan.

The salamander Hynobius yatsui from southwestern Japan was formerly regarded as a small-sized group of H. naevius, but has recently been resurrected as a distinct species. We investigated the phylogeography of H. yatsui from Kyushu Island using partial sequences of the mitochondrial cytochrome b gene. We detected 49 haplotypes in 181 individuals from 24 localities covering the entire geographic distribution of this species on Kyushu. These haplotypes were grouped into two lineages, a northern lineage from northern and central regions, and a southern lineage from the southern region; no haplotypes were shared between the lineages. We surmise that the divergence of the two lineages was induced by volcanic activity that started in the Beppu-Shimabara Graben, between the areas occupied by these two lineages. From the results of a nested clade phylogeographical analysis, we surmise that the high intrapopulation genetic variation observed in the non-volcanic Kyushu Mountains was generated by alternation of contiguous range expansion or long-distance dispersal, and isolation. The current distribution and the observed complicated genetic structures of H. yatsui in Kyushu seem to have been affected first by volcanic activities since the late Pliocene, but subsequent climatic oscillations during the Pleistocene may also have some effects, although it is impossible at this time to differentiate the effects of these two factors.

Estimation of the type locality of Hynobius naevius (Temminck and Schlegel, 1838), a salamander from Japan (Amphibia: Caudata)

Abstract A small Japanese salamander, Hynobius naevius, long considered a single species, has recently proven to include two groups (Group A=large type and Group B=small type) that are split at the species level. We compared the type series of H. naevius with specimens of the two groups to clarify which of them corresponds to true H. naevius, and to estimate the type locality of this species, which was not given in detail in its original description. Results of various morphological analyses altogether indicated that the type series belongs to Group A and that the population sample from Mt. Taradake, located on northwestern Kyushu, is most similar to the type series. Therefore, the type locality of the species is estimated to be in northwestern Kyushu. These results also indicate that Group B obviously represents a cryptic species whose scientific name remains to be determined.