Suyama Meegaskumbura

Patterns of reproductive-mode evolution in Old World tree frogs (Anura, Rhacophoridae)

The Old World tree frogs (Anura: Rhacophoridae), with 387 species, display a remarkable diversity of reproductive modes – aquatic breeding, terrestrial gel nesting, terrestrial foam nesting and terrestrial direct development. The evolution of these modes has until now remained poorly studied in the context of recent phylogenies for the clade. Here, we use newly obtained DNA sequences from three nuclear and two mitochondrial gene fragments, together with previously published sequence data, to generate a well‐resolved phylogeny from which we determine major patterns of reproductive‐mode evolution. We show that basal rhacophorids have fully aquatic eggs and larvae. Bayesian ancestral‐state reconstructions suggest that terrestrial gel‐encapsulated eggs, with early stages of larval development completed within the egg outside of water, are an intermediate stage in the evolution of terrestrial direct development and foam nesting. The ancestral forms of almost all currently recognized genera (except the fully aquatic basal forms) have a high likelihood of being terrestrial gel nesters. Direct development and foam nesting each appear to have evolved at least twice within Rhacophoridae, suggesting that reproductive modes are labile and may arise multiple times independently. Evolution from a fully aquatic reproductive mode to more terrestrial modes (direct development and foam nesting) occurs through intermediate gel nesting ancestral forms. This suggests that gel nesting is not only a possible transitional state for the evolution of terrestriality, but also that it is a versatile reproductive mode that may give rise to other terrestrial reproductive modes. Evolution of foam nesting may have enabled rhacophorids to lay a larger number of eggs in more open and drier habitats, where protection from desiccation is important. Terrestrial direct development allows frogs to lay eggs independent of bodies of water, in a diversity of humid habitats, and may represent a key innovation that facilitated the evolution of nearly half of all known rhacophorid species.

Systematic relationships and taxonomy of Suncus montanus and S. murinus from Sri Lanka.

Here we use nuclear and mitochondrial DNA sequence data, combined with morphometric analyses, to clarify the systematic relationships and taxonomy of two complex species of shrews, Suncus montanus and S. murinus, in Sri Lanka. We find that subspecies of S. murinus, Suncus murinus murinus from Anuaradhapura and S. m. caerulescens from Colombo, show little or no genetic difference in the mitochondrial (cytochrome-b and 16SrRNA) and nuclear (Rag 1, aldolase C and EF-1 alpha intron) genes, confirming their classification as a single species. However, two populations of S. murinus from Peradeniya and Udawalawe are identified as putative hybrids of S. murinus and S. montanus. Shrews collected from Peradeniya are best described as a population of S. murinus, but could be identified as S.m. kandianus using morphological features. Nuclear DNA sequence data places this population in a clade with other S. murinus, but mtDNA sequences of the population nests within a clade of S. montanus haplotypes. This discordant pattern of nuclear and mitochondrial genes suggests either hybridization between S. murinus and S. montanus or introgression of S. montanus mitochondrial DNA into S. m. kandianus. S. m. murinus from Udawalawe, which shows no distinct morphological difference from S. m. murinus from Anuradhapura, falls in the clade of S. murinus in both nuclear and mitochondrial trees. In the nuclear gene tree however, S. m.murinus from Udawalawe is placed as a sister taxon to the clade including other S. murinus. Rag 1 gene sequences in Udawalawe individuals suggest recombination of S. murinus and S. montanus DNA within the gene. However, additional nuclear genes are necessary to study the extent of the hybridization of S. murinus and S. montanus.