To survey the diversity of anuran species in Bangladesh, we compared mitochondrial 16S rRNA gene sequences (approximately 1.4 kbp) from 107 Bangladesh frog specimens. The results of genetic divergence and phylogenetic analyses incorporating data from related species revealed the occurrence of at least eight cryptic species. Hoplobatrachus tigerinus from two districts diverged considerably, indicating the involvement of a cryptic species. Two Fejervarya sp. (large and medium types) and Hylarana cf. taipehensis formed lineages distinct from related species and are probably new species. Microhyla cf. ornata differed from M. ornata with respect to type locality area and involved two distinct species. In addition, we found that Hylarana sp. and Microhyla sp. did not match congeners examined to date in either morphology or 16S rRNA sequence. The occurrence of M. fissipes was tentatively suggested. Consequently, at least, 19 species were found from Bangladesh in this study. These findings revealed a rich anuran biodiversity in Bangladesh, which is unexpected considering the rather simple topographic features of the country.

To elucidate the species composition, genetic divergence, evolutionary relationships, and divergence time of Hoplobatrachus and Euphlyctis frogs (subfamily Dicroglossinae, family Ranidae) in Bangladesh and other Asian countries, we analyzed the mitochondrial Cyt b, 12S, and 16S rRNA genes of 252 specimens. Our phylogenetic analyses showed 13 major clades corresponding to several cryptic species as well as to nominal species in the two genera. The results suggested monophyly of Asian Hoplobatrachus species, but the position of African Hoplobatrachus occipitalis was not clarified. Nucleotide divergence and phylogenetic data suggested the presence of allopatric cryptic species allied to Euphlyctis hexadactylus in Sundarban, Bangladesh and several parapatric cryptic species in the Western Ghats, India. The presence of at least two allopatric cryptic species among diverged Euphlyctis cyanophlyctis in Bangladesh, India, and Sri Lanka was also suggested. In some cases, our estimated divergence times matched the paleogeological events of South and Southeast Asian regions that may have led to the divergence of Hoplobatrachus and Euphlyctis taxa. Especially, land formation at Bangladesh (15-10Ma) may have allowed the spread of these frog taxa to Southeast Asian areas, and the aridification of central India (5.1-1.6Ma) might have affected the gene flow of widely distributed species. The present study revealed prior underestimation of the richness of the amphibian fauna in this region, indicating the possible occurrence of many cryptic species among these groups.

No abstract

The toads of the Bufo bufo species group are widely distributed in the Eurasian continent and Japanese Archipelago. In this study, we analyzed the mtDNA gene sequences of this species group and estimated the divergence time to clarify the evolutionary relationships and biogeography of toads distributed in the Far East and Europe. The phylogenetic tree indicated that this group produced Bufo bufo in Europe, whereas it produced B. japonicus in the Far East. B. japonicus was divided into three major clades corresponding to a group consisting of B. j. gargarizans in China, B. j. bankorensis in Taiwan, and B. j. miyakonis on Miyako Isl. and eastern and western groups of Japanese B. j. japonicus subspecies group. The eastern and western groups were divided into several subclades which tended to reflect the region-specific geographic distribution of all localities except B. j. japonicus from Hakodate. The estimated branching times of these clades suggest that geological events may have influenced the divergence of the toads distributed in the Far East and Europe.

Aim Pelophylax frogs in East Asia provide an opportunity to explore the impact of glacial cycling on demographic and genetic dynamics, because it has been suggested that they experienced distribution shifts and subsequent mtDNA introgression from Pelophylax plancyi to Pelophylax nigromaculatus in association with climatic oscillations. However, their evolutionary history, including the pattern of introgression, is incompletely understood. We used phylogenetic analyses based on multiple markers to address their evolutionary history, and palaeodistribution modelling to test whether the predicted distribution can explain the pattern of introgression suggested by molecular phylogenetics.Location East Asia, including far-eastern Russia, mainland China, the Japanese archipelago, the Korean Peninsula and Taiwan.Methods Ninety-nine samples of the Pelophylax nigromaculatus species complex were collected from 75 localities throughout the distributional range of each species. Phylogenetic analyses were performed with the mitochondrial cytochrome b (cytb) gene and six nuclear genes using two European Pelophylax frogs as outgroups. Additionally, palaeodistributions of P. nigromaculatus and P. plancyi were predicted using bioclimatic variables.Results Differences were observed between the mitochondrial and nuclear DNA trees in the phylogenetic position of P. plancyi. Similar phylogenetic discordance was also observed within P. nigromaculatus. Distribution modelling suggested that a considerable distributional shift of P. nigromaculatus occurred in association with glacial cycling and that the distributional range of P. plancyi was relatively narrow during glacial periods. Main conclusionsThe analyses detected five historical mtDNA introgression events and determined their directions, none of which had been deduced in previous studies. In association with glacial cycling, the distributional ranges of P. nigromaculatus and P. plancyi appear to have shifted repeatedly, resulting in multiple complex introgressions. By combining phylogenetic analyses with palaeodistribution modelling, our results supported the hypothesis that the history of mtDNA introgression among Pelophylax frogs was shaped by glacial cycling.

To elucidate genetic divergence and evolutionary relationship in Fejervarya cancrivora from Indonesia and other Asian countries, allozyme and molecular analyses were carried out using 131 frogs collected from 24 populations in Indonesia, Thailand, Bangladesh, Malaysia, and the Philippines. In the allozymic survey, seventeen enzymatic loci were examined for 92 frogs from eight representative localities. The results showed that F. cancrivora is subdivided into two main groups, the mangrove type and the large- plus Pelabuhan ratu types. The average Nel's genetic distance between the two groups was 0.535. Molecular phylogenetic trees based on nucleotide sequences of the 16S rRNA and Cyt b genes and constructed with the ML, MP, NJ, and BI methods also showed that the individuals of F. cancrivora analyzed comprised two clades, the mangrove type and the large plus Pelabuhan ratu / Sulawesi types, the latter further split into two subclades, the large type and the Pelabuhan ratu / Sulawesi type. The geographical distribution of individuals of the three F. cancrivora types was examined. Ten Individuals from Bangladesh, Thailand, and the Philippines represented the mangrove type; 34 Individuals from Malaysia and Indonesia represented the large type; and 11 individuals from Indonesia represented the Pelabuhan ratu / Sulawesi type. Average sequence divergences among the three types were 5.78-10.22% for the 16S and 12.88-16.38% for Cyt b. Our results suggest that each of the three types can be regarded as a distinct species.

The rice frog (Fejervarya limnocharis) species complex is widely distributed, from India to Japan, and most prevalently in Southeast Asia. Conspicuous morphological variation has been reported for this species complex throughout its distribution range. In the present study, we used mtDNA gene sequence and allozyme analyses to infer evolutionary affinities within this species complex using eight populations (Sri Lanka; Bangkok and Ranong in Thailand; Taiwan; and Hiroshima, Okinawa, Ishigaki and Iriomote in Japan). We also conducted crossing experiments among four populations from Japan, Thailand, and Sri Lanka in order to find out more about the reproductive isolating mechanisms that might exist among the East, Southeast, and South Asian populations of this species complex. The crossing experiments revealed that the Sri Lanka population is reproductively isolated from the Hiroshima, Bangkok, and Ranong populations by complete hybrid inviability, and that the Bangkok population may be reproductively isolated from the Hiroshima population by partial hybrid inviability. Thus, it is not unreasonable to regard the Sri Lanka population as a species separated from F. limnocharis. The mtDNA and allozyme data showed that the Ranong population is most closely related to the Bangkok population in nuclear genome, but more similar to the Okinawa and Taiwan populations in mtDNA genome. The present, preliminary survey may raise questions about the species status of these particular populations and also about the nature of the biological species concept.

Amphioxus or lancelets have been regarded as a key animal in understanding the origin of vertebrates. However, the evolutionary history within this lineage remains unexplored. As the amphioxus lineage has likely been separated from other chordates for a very long time and displays a marked left-right asymmetry, its evolutionary history is potentially helpful in better understanding chordate and vertebrate origins. We studied the phylogenetic relationships within the extant amphioxus lineage based on mitochondrial genomes incorporating new Asymmetron and Epigonichthys populations, and based on previously reported nuclear transcriptomes. The resulting tree patterns are consistent, showing the Asymmetron clade diverging first, followed by the Epigonichthys and Branchiostoma clades splitting. Divergence time estimates based on nuclear transcriptomes with vertebrate calibrations support a shallow diversification of the extant amphioxus lineage in the Tertiary. These estimates fit well with the closure of seaways between oceans by continental drift, ocean currents, and present geographical distributions, and suggest a long cryptic history from the origin of amphioxus to its most recent diversification. Deduced character polarities based on phylogenetic analyses suggest that the common ancestor of the extant amphioxus existed in a tiny epibenthic state with larva-like appearance of extant amphioxus, likely with ciliate epidermis.