The Out-of-India hypothesis: What do molecules suggest.

The remarkable geological and evolutionary history of peninsular India has generated much interest in the patterns and processes that might have shaped the current distributions of its endemic biota. In this regard the “Out-of-India” hypothesis, which proposes that rafting peninsular India carried Gondwanan forms to Asia after the break-up of Gondwana super continent, has gained prominence. Here we have reviewed molecular studies undertaken on a range of taxa of supposedly Gondwanan origin to better understand the Out-of-India scenario. This re-evaluation of published molecular studies indicates that there is mounting evidence supporting Out-of-India scenario for various Asian taxa. Nevertheless, in many studies the evidence is inconclusive due to lack of information on the age of relevant nodes. Studies also indicate that not all Gondwanan forms of peninsular India dispersed out of India. Many of these ancient lineages are confi ned to peninsular India and therefore are relict Gondwanan lineages. Additionally, for some taxa an “Into India” rather than “Out-of-India” scenario better explains their current distribution. To identify the “Out-of-India” component of Asian biota it is imperative that we understand the complex biogeographical history of India. To this end, we propose three oversimplifi ed yet explicit phylogenetic predictions. These predictions can be tested through the use of molecular phylogenetic tools in conjunction with palaeontological and geological data.

Primate numts and reticulate evolution of capped and golden leaf monkeys (Primates: Colobinae).

A recent phylogenetic study of langurs and leaf monkeys of South Asia suggested a reticulate evolution of capped and golden leaf monkeys through ancient hybridization between Semnopithecus and Trachypithecus .To test this hybridization scenario, I analysed nuclear copies of the mitochondrial cytochrome b gene (numts) from capped,golden and Phayre's leaf monkeys. These numts were aligned with mitochondrial cytochrome b sequences of various species belonging to the genera Semnopithecus and Trachypithecus .In the phylogenetic tree derived from this alignment,the numts fell into three distinct clades (A,B and C) suggesting three independent integration events.Clade A was basal to Semnopithecus, and clades B and C were basal to Trachypithecus. Among the numts in clades A and C were sequences derived from species not represented in their respective sister mitochondrial groups.This unusual placement of certain numts is taken as additional support for the hybridization scenario. Based on the molecular dating of these integration events,hybridization is estimated to have occurred around 7.1 to 3.4 million years ago.Capped and golden leaf monkeys might have to be assigned to a new genus to reconcile their unique evolutionary history. Additionally, northeast India appears to be a 'hot spot' for lineages that might have evolved through reticulate evolution.