Nayana Wijayathilaka

Ecomorphs result from divergent natural selection, leading to species-rich adaptive radiations. Identifying ecomorphs and the resulting adaptive radiations in frogs is challenging due to conserved morphology and high species diversity. In this study, we demonstrate the ecological and climate specializations that have driven the diversification of shrub frogs of the genus Pseudophilautus in Sri Lanka, a tropical continental island. We use a time-calibrated phylogeny, morphometric analyses, and climate-niche evolution, and identify five ecomorphological categories, including Tree-shrub, Rock-boulder, Leaf-litter, Habitat Generalists, and Canopy forms, and describe their evolution. Body size is the primary factor separating species, and specific body features correlate with habitat type. Ecomorphs likely evolved multiple times in disparate lineages, and in different regions and altitudes, during cold climatic periods owing to monsoon cycles resulting from the Himalayan-Tibetan orogeny. The common ancestor was a medium-sized, wet-adapted, tree-shrub habitat specialist which originated in the late Oligocene. Extreme size classes (diminutive leaf litter forms and large canopy forms) evolved recently and suggest that morphological disparity arose late in diversification, possibly aided by favorable climates. This work will facilitate understanding of adaptive radiations in frogs, which possibly will help uncover the prevalence of subtle adaptive radiations in frogs, just as in tailed-vertebrates.

Pseudophilautus conniffae from Lowland wet zone of Sri Lanka, was described as a new species in 2019. The validity of the new species was questionable and was often challenged as it shares strong morphological resemblance with P. limbus. Moreover, the phylogenetic placement of P. conniffae was unknown as no molecular data was available until now. Here, we generated 16S DNA sequences and re-examined the external morphological characters to assess its taxonomic distinctiveness. Pseudophilautus conniffae was recovered as being close to P. limbus with strong posterior probability and bootstrap support. The uncorrected pairwise genetic distance between P. conniffae and P. limbus was negligible, being less than 0.3% for the 16S gene fragment. Further two molecular species delimitation methods, ABGD and mPTP suggested that P. conniffae and P. limbus are a single operational taxonomic unit. The Principal Component Analysis of the morphometric characters also resulted in overlapping clusters. These results suggest that the newly described P. conniffae is not a valid species and we conclude that P. conniffae as a junior synonym of P. limbus.

Pseudophilautus pardus, was first described in 2007, based on a single specimen collected in Sri Lanka during the 19th century. Its absence in recent surveys suggested that the species was extinct. The distinctive spotted dorsal coloration, together with other morphological features, was used to distinguish it from congeners. In 2013, we discovered a specimen resembling the holotype of P. pardus in Samanala Strict Nature Reserve. A DNA analysis based on the 16S rRNA mt-DNA locus recovered a low uncorrected pairwise genetic distance of 0.77–0.96% between the recent example of ‘P. pardus’ and a congener, P. viridis. Molecular species delimitation methods suggest P. pardus and P. virids to be a single operational taxonomic unit. Morphological analyses using the freshly collected specimen, together with numerous photographic records show P. viridis to be a highly polychromatic species within which the coloration observed in P. pardus too occurs, though rarely. We conclude that P. pardus is a junior synonym of P. viridis.

Sri Lanka is an amphibian hotspot of global significance. Its anuran fauna is dominated by the shrub frogs of the genusPseudophilautus. Except for one small clade of four species in Peninsular India, these cool-wet adapted frogs, numbering some 59 extant species, are distributed mainly across the montane and lowland rain forests of the island. With species described primarily by morphological means, the diversification has never yet been subjected to a molecular species delimitation analysis, a procedure now routinely applied in taxonomy. Here we test the species boundaries ofPseudophilautusin the context of the phylogenetic species concept (PSC). We use all the putative species for which credible molecular data are available (nDNA–Rag-1; mt-DNA– 12S rRNA, 16S rRNA) to build a well resolved phylogeny, which is subjected to species delimitation analyses. The ABGD, bPTP, mPTP and bGMYC species delimitation methods applied to the 16S rRNA frog barcoding gene (for all species), 12S rRNA and Rag-1 nDNA groupedP.procaxandP.abundus;P.hallidayiandP.fergusonianus;P.reticulatusandP.pappilosus;P.pleurotaeniaandP.hoipolloi;P.hoffmaniandP.asankai;P.silvaticusandP.limbus;P.dilmahandP.hankeni;P.fulvusandP.silus.. Surprisingly, all analyses recovered 14 unidentified potential new species as well. The geophylogeny affirms a distribution across the island’s aseasonal ‘wet zone’ and its three principal hill ranges, suggestive of allopatric speciation playing a dominant role, especially between mountain masses. Among the species that are merged by the delimitation analyses, a pattern leading towards a model of parapatric speciation emerges–ongoing speciation in the presence of gene flow. This delimitation analysis reinforces the species hypotheses, paving the way to a reasonable understanding of Sri LankanPseudophilautus, enabling both deeper analyses and conservation efforts of this remarkable diversification.http://zoobank.org/urn:lsid:zoobank.org:pub:DA869B6B-870A-4ED3-BF5D-5AA3F69DDD27.

Acoustic inventory of Sri Lankan amphibians is still in a primitive stage. So far, only 20 amphibian species are known acoustically and are about 16% of the island amphibian fauna. Altogether, twelve publications provide primary acoustic characters, yet the majority of them are not quantitative. Bioacoustics is a powerful tool that can use in many disciplines, including taxonomy and conservation. This work emphasises that the current knowledge on the vocalisation of Sri Lankan amphibians is not adequate and highlighted its applications towards conservation and planning.