An integrative approach to infer systematic relationships and define species groups in the shrub frog genus Raorchestes, with description of five new species from the Western Ghats, India

The genus Raorchestes is a large radiation of Old World tree frogs for which the Western Ghats in Peninsular India is the major center for origin and diversification. Extensive studies on this group during the past two decades have resolved long-standing taxonomic confusions and uncovered several new species, resulting in a four-fold increase in the number of known Raorchestes frogs from this region. Our ongoing research has revealed another five new species in the genus, formally described as Raorchestes drutaahu sp. nov., Raorchestes kakkayamensis sp. nov., Raorchestes keirasabinae sp. nov., Raorchestes sanjappai sp. nov., and Raorchestes vellikkannan sp. nov., all from the State of Kerala in southern Western Ghats. Based on new collections, we also provide insights on the taxonomic identity of three previously known taxa. Furthermore, since attempts for an up-to-date comprehensive study of this taxonomically challenging genus using multiple integrative taxonomic approaches have been lacking, here we review the systematic affinities of all known Raorchestes species and define 16 species groups based on evidence from multi-gene (2,327 bp) phylogenetic analyses, several morphological characters (including eye colouration and pattern), and acoustic parameters (temporal and spectral properties, as well as calling height). The results of our study present novel insights to facilitate a better working taxonomy for this rather speciose and morphologically conserved radiation of shrub frogs. This will further enable proper field identification, provide momentum for multi-disciplinary studies, as well as assist conservation of one of the most colourful and acoustically diverse frog groups of the Western Ghats biodiversity hotspot.

Hot spring frogs (Buergeria japonica) prefer cooler water to hot water

"Hot spring frog" is an informal name used for the Japanese stream tree frog (Buergeria japonica), which is widely distributed in Taiwan and the Ryukyu Archipelago in Japan. Some populations of the species are known to inhabit hot springs. However, water temperature can be extremely high around the sources of hot springs. Thus, it is questionable whether B. japonica selectively inhabits such dangerous environments. To address this question, we conducted a series of observations of water temperature preferences of a hot spring population of B. japonica in Kuchinoshima Island in Japan: (a) a field observation of tadpole density in water pools of different temperatures, (b) a field observation of water temperatures where adult males appear for breeding, and (c) an indoor observation of water temperatures selected by adult females for oviposition. As a result, tadpoles showed a higher density in cooler water. Adult males avoided water pools hotter than 37°C, and adult females selected cooler pools for oviposition. Camera records also showed that adult individuals tend to appear around cooler pools. Thus, we did not find any support for the hypothesis that hot spring frogs prefer hot water. Conversely, they apparently tended to prefer cooler water if it was available. Water temperatures around the sources of the hot spring exceed thermal tolerances of the species and could be a strong selective pressure on the population. Thus, the ability to sense and avoid lethal temperatures may be a key ecological and physiological characteristic for the species that inhabit hot springs.

An integrative phylogenomic approach illuminates the evolutionary history of Old World tree frogs (Anura: Rhacophoridae)

Rhacophoridae are one of the most speciose and ecologically diverse families of amphibians. Resolution of their evolutionary relationships is key to understanding the accumulation of biodiversity, yet previous hypotheses based on Sanger sequencing exhibit much discordance amongst generic relationships. This conflict precludes the making of sound macroevolutionary conclusions. Herein, we conduct the first phylogenomic study using broad-scale sampling and sequences of 352 nuclear DNA loci obtained using anchored hybrid enrichment targeted sequencing. The robust time-calibrated phylogenetic hypothesis clarifies several long-disputed relationships and facilitates the testing of evolutionary hypotheses on spatiotemporal diversification and reproductive modes. The major extant lineages of Rhacophoridae appear to have radiated in mainland Asia, and the spatiotemporal process corresponds with several common accumulations of biodiversity in Asia. Analyses do not detect any case of "Out of Himalaya" in Rhacophoridae. All transitions of reproductive modes appear to have evolved in an ordered, gradual sequence associated with gaining independence of standing water for larval development. The different reproductive modes are phylogenetically conserved and the completion of their transitions appear to have occurred over a period of ~30 Ma, which does not fit a pattern of a rapid burst of diversification. Innovations in reproductive modes associate statistically with the uneven distribution of species-richness between clades, where higher diversification is linked to increased terrestrial modes of reproduction. These results strengthen the hypothesis that breeding innovations drive diversification by providing new opportunities for ecological release and dispersion.

(Monogenea, Polystomatidae) with the description of three new species and reassignment of eight known Polystoma species from Asian frogs (Anura, Rhacophoridae)

The polystomes (Monogenea, Polystomatidae) radiated across semi-aquatic tetrapods including all three amphibian orders, freshwater turtles and the hippopotamus. Prior to this study, phylogenetic analyses revealed that the most diverse and widespread genus, Polystoma, was not monophyletic; a lineage comprising four undescribed species from the bladder of Zhangixalus spp. (Rhacophoridae) in Asia occupied a deep phylogenetic position. Regarding vicariance biogeography and molecular dating, the origin of this lineage is correlated with the breakup of Gondwanaland in the Mesozoic period. Based on a Bayesian analysis of four concatenated genes (18S, 28S, COI and 12S) and morphological evidence, one new genus, Indopolystoma n. gen., and three new species, sampled in Japan and China, are described here: Indopolystoma viridi n. sp. from Z. viridis of Japan, Indopolystoma elongatum n. sp. from Z. arboreus of Japan, and Indopolystoma parvum n. sp. from Z. omeimontis of China. Indopolystoma is unique amongst polystome genera infecting anurans by possessing a small haptor relative to the body size, posteriormost marginal hooklet C1 much bigger than hooklets C2–C8 with conspicuous broad blade and guard and a pair of hamuli lacking a deep notch. Eight species of Asian Polystoma, all from rhacophorids, are transferred as Indopolystoma carvirostris (Fan, Li & He, 2008) n. comb., I. hakgalense (Crusz & Ching, 1975) n. comb., I. indicum (Diengdoh & Tandon, 1991) n. comb., I. leucomystax (Zhang & Long, 1987) n. comb., I. mutus (Meng, Song & Ding, 2010) n. comb., I. pingbianensis (Fan, Wang & Li, 2004) n. comb., I. rhacophori (Yamaguti, 1936) n. comb., and I. zuoi (Shen, Wang & Fan, 2013) n. comb.

Reproduction and metamorphosis in the Myristica Swamp tree frog, Mercurana myristicapalustris (Anura: Rhacophoridae)

The reproductive biology of the Myristica Swamp tree frog (Mercurana myristicapalustris), a monotypic rhacophorid frog endemic to the foothills of the Western Ghats mountains of India, has remained unknown since the description of the genus and species. We monitored individuals from parental generation amplexus to the completion of offspring generation tadpole metamorphosis. Surprisingly, our observations revealed that this species exhibits many previously unknown characteristics, including the first ever record of the female, and a diverse call repertoire, consisting of five different call types (the functions of which remain incompletely known). We were also able to determine that reproductive activity peaked during the late pre-monsoon season, that males engaged in intraspecific aggressive encounters to occupy and to defend desirable territories, and that oviposition took place in terrestrial nests made by females. Embryonic development in the unattended nest was followed by tadpole development, which concluded within 40 days. The specific breeding mode employed by Mercurana, which restricts its range to the endangered Myristica swamp ecosystem, likely renders it susceptible to multiple threats, which should be considered jointly in future conservation planning.

Geological data indicate that the interpretation for the age-calibrated phylogeny for the Kurixalus-genus frogs of South, South-east and East Asia (Lv et al., 2018) needs to be rethought

Recently, Lv et al. (2018) published an age-calibrated phylogenetic tree for the Kurixalus frogs, members of which occur across parts of South, South-east and East Asia. A clade on Taiwan, represented by Kurixalus idiootocus and the Kurixalus eiffingeri species complex, is deemed to have been resident since the middle Cenozoic; its closest congeners are in southern Indochina (not in the adjacent parts of south-east China), and the split between the two is dated at 32.8 Ma. Furthermore, a sub-population of Kurixalus eiffingeri is believed to have colonized islands in the western Ryukyus c. 13.5 Ma. There is, however, a problem with this scenario: the landmass regarded as modern-day Taiwan has existed only for 4-5 million years (it results from a young and ongoing tectonic-plate collision). Assuming the Kurixalus phylogeny and the dating of its branchings are correct, then a palaeobiogeographical scenario involving an older, alternative land surface with later transfer to Taiwan, possibly involving over-water dispersal, would reconcile the biology, but testing this may be difficult/impossible. If the ages of the nodes in the proposed tree are found to be significantly overestimated, the geology and biology might more easily be accommodated.

The complete mitochondrial genome of Rhacophorus dennysi (Anura: Rhacophoridae) and phylogenetic analysis

Rhacophorus dennysi is one species of the family Rhacophoridae. In this study, we sequenced the complete mitochondrial genome of R. dennysi. The complete mitochondrial genome of R. dennysi was 17 572 bp in length (GenBank accession number KT191129). Similar to the typical mtDNA of amphibians, the complete mtDNA sequence of R. dennysi contained two rRNA genes, 22 tRNA genes, 13 protein-coding genes (PCGs), and one D-loop region. The complete mitogenome sequence data in R. dennysi would provide a basis and important molecular data for studying the phylogenetic relationship, molecular identification and evolutionary analysis in anura species. The results will be useful for the detailed study of mitogenome evolution and the phylogenetic relationships among the orders in the class Rhacophoridae.