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

Can’t see the wood for the trees? Canopy physiognomy influences the distribution of peninsular Indian flying lizards

“…11-5 mya), resulted in the fragmentation of these forests and the spread of drier biomes (Morley, 2000;Patnaik et al, 2012;Pound et al, 2012). While such forest fragmentation resulted in climate-induced vicariance of many faunal groups (Biswas & Karanth, 2021), there is sufficient evidence to suggest continued dispersal in some of these organisms well into the Pliocene (5.33-2.58 mya) and into the Quaternary (<2.58 mya) (Vijayakumar et al, 2014). Therefore, many biogeographers argue that the valleys in the Western Ghats, and the intervening arid plains that separate the Western and Eastern Ghats, retained permeable causeways until very recently (Chaitanya et al, 2019;Hegde et al, 2020;Vijayakumar et al, 2014).…”

“…The Western Ghats mountain complex in peninsular India is characterized by three prominent biogeographic discontinuities-the Shencottah pass, the Palghat gap and the Goa gap (Figure 1) which act as either barriers or conduits of dispersal depending on the ecology of the organism (Bhimachar, 1945;Biswas & Karanth, 2021;Mani, 1974b). While these barriers to dispersal (and therefore to gene 500 million years ago (mya) as a result of shearing and erosion (D' Cruz et al, 2000;Soman et al, 1990;Subramaninan & Muraleedharan, 1985).…”

“…Some lineages could traverse, colonize and diversify across the Goa gap while others could not overcome this environmental barrier. While the Palghat and Shencottah valleys have caused cladogenesis in organisms due to climate‐induced vicariance, diversification across the Goa gap seems to have been governed by the ecological ability of certain lineages to disperse through and colonize it (Biswas & Karanth, 2021; Ramachandran et al, 2017).…”

“…The Western Ghats mountain complex in peninsular India is characterized by three prominent biogeographic discontinuities—the Shencottah pass, the Palghat gap and the Goa gap (Figure 1) which act as either barriers or conduits of dispersal depending on the ecology of the organism (Bhimachar, 1945; Biswas & Karanth, 2021; Mani, 1974b). While these barriers to dispersal (and therefore to gene flow) have led to cladogenesis in several vertebrate groups (see the examples in Biswas & Karanth, 2021), the underlying biogeographic mechanisms at play have largely been different for the Palghat and Shencottah valleys vis‐à‐vis the Goa gap.…”

“…The Goa gap (~15.8°N), on the other hand, tracks the southern margins of the Deccan Traps—a large igneous region formed by a series of volcanic eruptions during the KT boundary (~66 mya) which had profound effects on biodiversity in the region and possibly led to successional vegetation cycles and regional extirpation events (Dzombak et al, 2020; Glasby & Kunzendorf, 1996; Knight et al, 2003). The Goa gap is not a topographic obstacle, but an invisible, yet effective barrier occurring at the cusp of a wet–dry gradient in the Western Ghats (Barboni et al, 2003; Biswas & Karanth, 2021; Ramachandran et al, 2017). Studies of the evergreen forests of the Western Ghats and their distributions indicate that the Goa gap also serves as a vegetational transition zone (Pascal, 1988; Qureshi, 1965; Reddy et al, 2016).…”