PTERIDOPHYTES OF WESTERN GHATS

The Western Ghats of the Indian peninsula constitute one of the 34 global biodiversity hotspots along with Sri Lanka, on account of exceptional levels of plant endemism and by serious levels of habitat loss (Conservation International, 2005). The rugged range of hills stretching for about 1600 km along the west coast from south of Gujarat to the end of the peninsula (lat. 8° and 21° N and long. 73° and 78° E), is interrupted only by a 30 km break in Kerala, the Palghat Gap (Radhakrishna, 2001). Covering a geographical area of about 160,000 km2, the Western Ghats have an average height of 900 m, with several cliffs rising over 1000 m. The Nilgiri Plateau to the north and Anamalais to the south of the Palghat Gap exceed 2000 m in many places. Towards the eastern side the Ghats merge with the Deccan Plateau which gradually slopes towards the Bay of Bengal. The Western Ghats of Karnataka state encompasses the areas of Uttara Kannada, Shimoga, Chikmagalur, Hassan, Kodagu and Dakshina Kannada. These areas together form the Central Western Ghats, a region endowed with a wide range of vegetation types and extremely rich biodiversity.

The flora of Western Ghats comprises about 12,000 known species ranging from unicellular cyanobacteria to angiosperms. Of this spectrum the flowering plants with over 4000 species,with about 1,500 endemics, constitute about 27% of Indian flora. The Western Ghats also supports a diverse fauna which include 508 species of birds, followed by fishes (218 species), reptiles (157 species), mammals (137 species), and amphibians (126 species). Many faunal species are also endemic to the Western Ghats with the amphibians ranking highest (78%) followed by reptiles (62%), fishes (53%), mammals (12%) and birds (4%). (Daniels, 2003; Gururaja, 2004; Sreekantha, et al.,  2007).

The Western Ghats form one of the important habitats for pteridophytes due to the presence of perennial streams, evergreen forests, grasslands and many other habitats which support a luxuriant growth of ferns and fern-allies. Approximately 320 species of ferns and fern-allies have found their abode in the varied habitats of Western Ghats with their diversity increasing in the north-south direction, obviously due to the more number of rainy months and higher altitudes with cooler climate that the south has. As one proceeds towards the northern part of the escarpment, the number of rainy days decrease leading to the decrease in the extent of evergreen forests, perenniality of streams and decline in overall moisture in the climate.

The major families of the pteridophytes of the Western Ghats are Thelypteridaceae, Aspleniaceae, Pteridaceae, Selaginellaceae, Polypodiaceae, etc. Western Ghats also support luxuriant growth of important endemic species such as Cyathea nilgirensis, Polystichum manickamii, Bolbitis semicordata, Osmuda huegeliana, etc. and endangered species such as Helminthostachys zeylanica, Grammitis medialis, Tectaria zeylanica, Psilotum nudum, etc. in their preferred microclimates.