Reptile Communities of Agasthyamalai Hills with Emphasis on Distribution along Elevation Gradient

Abstract

Unravelling the mechanisms behind the spatial distribution of species has been a challenging endeavour for ecologists (Lomolino & Brown, 2004). Many attempts have been made to study the spatial gradients in species richness (Darwin, 1859; Wallace, 1876; Whittaker, 1960; Brown, 1971; Rahbek, 1995) which were carried out mainly to explore the underlying mechanisms of species distributions across different geographical zones. These explorations have indicated the importance of evolutionary, geographical and environmental factors in determining species distributions. Consequently, understanding species distribution patterns became a central theme in community ecology, and a prerequisite for conservation planning (Vetaas & Grytnes, 2002). The latitudinal variations in species richness is a well known distribution pattern where more species tend to occur in the tropics than in temperate zones (Brown, 1995). Comparable patterns have been found along mountain ranges as well, where the species richness tends to decrease with increasing elevations. These patterns were initially explained as a phenomenon that happens in response to the extreme climatic conditions in higher elevations similar to that in temperate zones (Stevens, 1992). In addition, patterns such as mid-elevation peaks in species richness along elevation gradients have also been reported for various taxa.