Understanding past climatic factors on biogeographic patterns in amphibians and freshwater snails
Climate can have a significant influence on the distribution of biodiversity. The Indian monsoons, which formed 7-12 million years ago, could have influenced the diversification in amphibians of the bio-diverse Western Ghats. This project tested the above hypotheses using molecular data for over 150 endemic species across seven families of amphibians. The results indicated that genera Micrixalus, Indosylvirana and Raorchestes diversified after the Indian monsoon strengthened. These genera are either post-monsoon breeders (Micrixalus and Indosylvirana), terrestrial breeders (Indirana), or develop directly, bypassing tadpole phase (in the case of Raorchestes). Comparatively, other families, indicated by the study, had evolved early during the Miocene and post mid-Miocene optima. The Western Ghats is also home to several species of snails including the Genus Cremnoconchus, a uniquely freshwater mollusc belonging to the family Littorinidae, which is entirely marine. The project will investigate whether sea level changes in the last 100 million years are responsible for the diversification of Cremnoconchus in freshwater habitats of the Western Ghats. At present, central and northern Western Ghats house 13 species of snails, with nine species restricted to central and four to the northern Western Ghats. The project used preliminary molecular studies using both nuclear and mitochondrial markers to study how these species would have evolved.