Mamoru Toda

Phylogeny, taxonomy, and biogeography of the oriental pitvipers of the genus Trimeresurus (Reptilia: Viperidae: Crotalinae): a molecular perspective.

Abstract Based on sequence variation in 806 bp of the mitochondrial 12S rRNA gene, phylogenetic relationships were inferred for 14 species of Trimeresurus (sensu lato) including all East Asian members. Samples analyzed also included representatives of all assemblages of species that are frequently treated as separate genera except for T. mangshanensis, a type species of the recently described monotypic genus Ermia. Results support some previous accounts chiefly from morphological studies, such as distinct divergence of T. wagleri from the remainder, and monophyly of T. mucrosquamatus, T. flavoviridis, T. jerdonii, T. elegans and T. tokarensis. On the other hand, our results negated a putative close affinity of T. monticola and T. okinavensis, and indicated the sister relationship of the latter with T. gracilis. Phylogenetic relationships revealed in this study suggested that the genus Trimeresurus dispersed into the Ryukyu region at least three times, and that T. flavoviridis and T. tokarensis from the central Ryukyus constitute a relict clade.

Parapatric distribution of the lizards Plestiodon (formerly Eumeces) latiscutatus and P. japonicus (Reptilia: Scincidae) around the Izu Peninsula, Central Japan, and its biogeographic implications.

Abstract The scincid lizard Plestiodon latiscutatus is found in the Izu Islands and Izu Peninsula of central Japan, whereas P. japonicus, a close relative, is found over the entire main island group of Japan, except the Izu Peninsula. The precise area of occupancy of these species was surveyed around the Izu Peninsula. Species identification was made through comparison of mitochondrial DNA partial sequences of specimens from the Izu Peninsula with those from the other regions, since morphological differences between these species have not yet been characterized. This study determined that these species are deeply diverged from each other in mitochondrial DNA sequence, and that the ranges of these species overlap only in a narrow zone. The results imply that gene flow between these species, if any, is restricted to a low level, without physical barriers. The boundary between the geographic ranges of these species was established as occurring along the lower Fuji River, Mt. Fuji, and the Sakawa River. This region is concordant with that of the old sea that is assumed to have separated the Izu Peninsula from other parts of the Japanese main island group until the middle Pleistocene. This pattern suggests that P. latiscutatus and P. japonicus were differentiated allopatrically before the connection of land areas of the Izu Peninsula and Honshu, the main island of Japan, and come into secondary contact through this connection. Thus, the species boundary is likely to have been maintained in situ, without physical barriers, since the secondary contact in the middle Pleistocene.

Clonal Composition of the Parthenogenetic Gecko, Lepidodactylus lugubris, at the Northernmost Extremity of Its Range

Abstract The mourning gecko, Lepidodactylus lugubris, is an all-female parthenogenetic species widely distributed in tropical and subtropical regions. We examined clonal diversity of L. lugubris in southern Japan, the northernmost extremity of the species range. Results indicated that the assemblages of the Ogasawara Islands are composed solely of diploid clone A, which may have originated from artificial transportation after World War II. Assemblages of L. lugubris in the Ryukyu Archipelago were composed solely of triploid clone C. This, along with literature records, suggests that the gecko recently colonized the Ryukyu Archipelago on limited opportunities from limited sources. Samples from the Daito Islands included both diploid and triploid individuals representing one and 11 different clones, respectively. Except for one triploid clone (clone B), these clones were most likely to be endemic to the Daito Islands. Analyses of genotypic pattern suggest that most of the putative endemic triploid clones of the Daito Islands originated from iterative crosses between sympatric diploid clones and males of closely related bisexual species that were most likely extirpated subsequently.

A New Species of Frog Allied to Fejervarya limnocharis from the Southern Ryukyus, Japan (Amphibia: Ranidae)

ABSTRACT The populations of a frog long identified as Fejervarya limnocharis from the Southern Ryukyus (=Sakishima in conventional regional name), Japan, considerably differ genetically and morphologically from the topotypic population of the species from Java. These Southern Ryukyu populations are therefore judged to represent a distinct biological species, which is described here as Fejervarya sakishimensis. This new species differs from F. limnocharis in larger snout-vent length (SVL). Also, it is distinguished from the latter in shorter head and tibia, smaller eye and narrower internarial space, all relative to SVL, and larger ratio of the first toe length to the inner metatarsal tubercle. From F. multistriata, F. sakishimensis differs by relatively larger tympanum, wider head, upper eyelid and anterior and posterior spaces of eyes, and longer forelimb and first toe, besides larger SVL. Furthermore, F. sakishimensis has a larger body, and relatively shorter head, tibia and hindlimb than F. iskandari. Also, this species is differentiated from all other nominate taxa of the F. limnocharis complex by a combination of some morphological characteristics.

Extensive Natural Hybridization Between Two Geckos, Gekko tawaensis and Gekko japonicus (Reptilia: Squamata), Throughout Their Broad Sympatric Area

The status of natural hybridization between the two Japanese geckos, Gekko tawaensis and Gekko japonicus, was surveyed by use of 15 diagnostic allozyme loci. Of 438 specimens examined, 9 were identified as Fl, 1 was a first backcross with G. japonicus, and 15 were identified as more successive generations. Hybridizations were detected at 7 of the 15 localities interspersed throughout a broad sympatric area of the two species, forming a mosaic hybrid zone. A comparison of species–hybrid composition between 2-year samples from a single locality and a 5-year interval showed no evidence for progressive introgression or establishment of a hybrid swarm, despite constant emergences of Fl hybrids. Nonprevalence of the hybrid genotypes was also indicated by the analysis using hybrid index scores for all other localities examined. These results suggest that strong selection acts against hybrid genotypes. Morphological features of hybrid individuals were also provided.

Allozyme Variation in the Camaenid Tree Snails Amphidromus atricallosus (Gould, 1843) and A. inversus (Müller, 1774)

Abstract We examined allozyme variation in two camaenid tree snails, Amphidromus atricallosus and A. inversus, across two principal regions of Thailand and from Singapore, plus for A. inversus, one site in peninsular Malaysia. Using horizontal starch gel electrophoresis, 13 allozyme loci (11 polymorphic) were screened for A. atricallosus and 18 (5 polymorphic) for A. inversus. Heterozygosity was higher in A. atricallosus (Hexp=0.018–0.201, mean=0.085) than in A. inversus (Hexp=0–0.023, mean= 0.002). Genetic heterogeneity among samples was higher in A. inversus (Fst=0.965) than in A. atricallosus (Fst=0.781). Within A. atricallosus, populations were more differentiated in southern Thailand (Fst=0.551) than in eastern Thailand (Fst=0.144). The high Fst and low Hexp in populations of A. inversus suggest that this species is likely to have experienced a series of strong bottlenecks, perhaps occurring chiefly on offshore continental-shelf islands. The low Fst values of A. atricallosus in eastern Thailand suggest frequent gene flows among populations in this region. The southern and eastern samples of A. atricallosus exhibited fixed allele differences at four loci and great genetic distance (Neis D=0.485–0.946), suggesting that these two samples may actually represent, or else be evolving into, separate species.

Body Temperature of Subtropical Snakes at Night: How Cold is Their Blood?

Abstract: Thermal biology of snakes has been extensively studied, but vast majority of them deals with diurnal species distributed in temperate regions. During a long-term field study of a pitviper on subtropical Okinawa Island, the Ryukyu Archipelago, Japan, we had an opportunity to obtain body temperature data from six syntopic species of snakes belonging to the families Colubridae, Xenodermidae, Viperidae, and Elapidae that are active at night there. Mean body temperature of those nocturnally active snakes over a year was relatively low, ranging from 17.7 to 22.3°C, although research effort was largely biased to the cooler period of the year. Lowest body temperature of the six species ranged from 10.9 to 20.0°C. Irrespective of species, body temperature was highly correlated with both ambient air and substrate temperatures. Importance of future research on the activity of subtropical, nocturnal snakes under low temperature is briefly discussed.