Thesis Colloquium at CES on 30 May 2017 at 11:00 am titled "Systematics and comparative biogeography of vine snakes (Genus: Ahaetulla, Family: Colubridae) and pit vipers (Genus: Trimeresurus, Family: Viperidae) in Peninsular India" by Ashok Kumar Mallik f
The evolution and biogeography of various taxa in Peninsular India are of particular interest as this region, a Gondawanan fragment, is critical to our understanding of historical biogeography in the Oriental realm. Over the past decade, molecular tools have enabled testing of alternative historical scenarios of faunal exchange and consequent biogeographic patterns. The snakes of Peninsular India, despite their spectacular diversity, remain poorly known with regard to their biogeographic affinities. While most Indian snakes are considered to be Malayan relicts, this hypothesis remains unexplored. Hence, we explored historical patterns of dispersal and diversification within Peninsular India using two distantly related snakes with broad differences in ecology and biology; an arboreal, non-venomous genus, Ahaetulla (vine snakes), belonging to the family Colubridae, and the genus Trimeresurus (pit vipers) a group of terrestrial and arboreal, venomous snakes belonging to the family Viperidae.
First, using an extensive taxon sampling of snakes from Peninsular India and adjoining Northeast India, we delimited species using a coalescent method and a multi-criteria approach including genes, geography and morphology. The results reveal the presence of several new lineages of snakes, including morphologically cryptic lineages, in both genera. Second, using mitochondrial and nuclear DNA, we reconstructed the phylogenies of the delimited lineages. In vine snakes, we discovered a deeply divergent lineage (Proahaetulla gen. nov.) from the southern Western Ghats, that is sister to all remaining members of Ahaetulla. In Trimeresures, we recovered multiple clades, one of which is predominantly peninsular Indian with a few Southeast Asian lineages. Third, we tested for clade congruence in patterns of diversification and dispersal using ancestral range reconstruction of geographical ranges. In contrast to earlier hypotheses, Peninsular India emerged as a centre of snake diversification and Western Ghats as a major centre of in-situ radiation for both clades. Patterns of dispersal show signatures of congruence and contrast between the clades, with the Western Ghats acting as a major source for colonisation of ancestral lineages into the arid regions in Peninsular India and adjoining Sri Lanka as well as Southeast Asian regions.