Role of Geographical Gaps in the Western Ghats in Shaping Intra- and Interspecific Genetic Diversity

Gaps or wide valleys in mountain systems are of much interest to biogeographers and evolutionary biologists since they shape species distributions as well as inter- and intraspecific genetic diversity. The Western Ghats, a hill range that runs parallel to the west coast of India, is one of the biodiversity hotspots with the highest level of endemism in the Indian Subcontinent. This hill range is interrupted by at least three large valleys or gaps, namely Palghat, Shencottah and Goa Gaps. Here, we review studies undertaken in the last two decades that have looked at the role of these gaps in shaping inter and intraspecific genetic diversity in different taxa. Overall, our review suggests that the Palghat gap appears to be a major barrier for a range of taxonomic groups, followed by Shencottah and Goa Gaps to a lesser extent. These patterns are consistent with the depth and width of these gaps, as Palghat gap is the deepest and widest among these gaps. Importantly, all of these divergences across the gaps have occurred long after the formation of these gaps. Therefore, geology-mediated vicariance can be ruled out. Furthermore, in some groups, the ecology, life-history traits, historical biogeography of the taxa in question better explain their distributions.