Thursday, September 12, 2013

Rhacophorid frog phylogeny on Borneo

Kurixalus appendiculatus
Rhacophoridae is a major clade of Afro-Asian tree frogs, that has radiated into many different niches. Rhacophorids contribute significantly to the high species richness and reproductive diversity of Sundaland vertebrates. Nonetheless, rhacophorid evolution, especially on Borneo, has not been studied within a phylogenetic context. In a new study Hertwig et al. examine the phylogenetic relationships of 38 (of 41 known) Bornean  rhacophorid frogs, in combination with data from previous phylogenetic studies. In the final super matrix of 91 species, they analyse sequence data from two mitochondrial and three nuclear genes. The results show the genus Rhacophorus as a paraphyletic  assemblage. Consequently they transfer Rhacophorus appendiculatus and R. kajau to two other genera and propose the new phylogeny-based combinations- Kurixalus appendiculatus and Feihyla kajau, respectively. Surprisingly they also found Theloderma moloch, a northeast Indian species, is an independent lineage of frogs within the  rhacphorid clade, separate from the other species of Theloderma (asperum, corticale, and rhododiscus) in the study. They also use their phylogenetic hypotheses to reconstruct the evolution of reproductive modes in rhacophorid tree frogs. Direct development to the exclusion of a free larval stage evolved twice independently, once in an ancestor of the Pseudophilautus + Raorchestes clade in India and Sri Lanka, and once within Philautus in Southeast Asia. The deposition of egg clutches covered by a layer of jelly in Feihyla is also present in F. kajau and thus confirms its generic reassignment. The remarkably high diversity of rhacophorid tree frogs on Borneo is the outcome of a complex pattern of repeated vicariance and dispersal events caused by past changes in the climatic and geological history of the Sunda shelf. The authors also identified geographic clades of closely related endemic species within Rhacophorus and Philautus, which result from local island radiations on Borneo.

Citation
Hertwig ST,  Schweizer M, Das I, Haas A. 2013. Diversification in a biodiversity hotspot – The evolution of Southeast Asian rhacophorid tree frogs on Borneo (Amphibia: Anura: Rhacophoridae). Molecular Phylogenetics and Evolution 68: 567–581.

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