INTRODUCTION

The Western Ghats, running almost parallel to the west coast of India, along with Sri-Lanka is one among 34 biodiversity hotspots of the world. It also features among the 200 globally most important ecoregions in the world (Olson and Dinerstien 1998). Covering an area of about 160,000 km², this rugged range of hills stretches for about 1600 km from the south Gujarat in the north to nearly the southern tip of the In-dian Peninsula (8°N-20°N). The complex ge-ography, wide variations in annual rainfall from 1000-6000 mm, and altitudinal decrease in tem-perature, coupled with anthropogenic factors, have produced a variety of vegetation types in the Western Ghats. Based on various field-based analysis of vegetation communities and satel-lite image interpretation, there are four basic forest types found in the Western Ghats: ever-green, semi-evergreen, moist deciduous and dry deciduous. The majority of the area under moist forest types falls within the southern states of Kerala and Karnataka which together account for about 80% of evergreen forest and 66% of moist deciduous forests in the entire Western Ghats (IIRS 2002). The other important veg-etation types include scrub jungles, savannahs and shola forests, peat bogs and Myristica swamps. Nearly 4000 species of flowering plants or about 27% of the country’s total species are known from the Ghats. Of 645 species of ever-green trees (>10 cm dbh (Diameter at breast height), about 56% is endemic to the Ghats (WGEP 2011; Nair and Daniel 1986). Faunal endemism is also high, in the order of amphib-ians (78%), reptiles (62%), fishes (53%), mam-mals (12%) and birds (4%) (Daniels 2003; Gururaja 2004; Sreekantha et al. 2007).

Forest fragmentation in tropical rainforests has been considered as one of the greatest threats to the biodiversity, especially in such species rich ecosystems (Myers 1986; Whitmore and Sayer 1992). The Western Ghats with exemplary biodiversity, also faces severe threats from various anthropogenic activities due to unplanned developmental activities, conversion of native vegetation with plantations of exotic species and encroachment of forests leading to fragmentation of habitats. The disturbances in the forest ecosystems play a central role in shaping the species composition in forests (Canham and Marks 1985) as they directly influence the community and population dynamics by altering resource availability (Denslow et al. 1998), by causing mortality and providing opportunities for recruitment (Canham and Marks 1985), and by influencing the relative competitive status of individuals (Sousa, 1984).The disturbances associated with anthropogenic activities have overruled natural disturbances in many tropical landscapes and once the human induced disturbance starts in a system the degradation will continue pending introduction of some protective measures (Anitha et al. 2009). It has been estimated that between 1920 and 1990, the forest cover in Western Ghats has declined by about 40%, resulting in a four-fold increase in the number of fragments and an 83% reduction in size of forest patches (Menon and Bawa 1997).