PTERIDOPHYTES OF CENTRAL 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 Western Ghats form one of the important habitats for pteridophytes due to the presence of perennial streams, evergreen forests, grasslands and many other habitats, all supporting ferns and fern-allies and some , the damper ones their luxuriant growth. Approximately 320 species of ferns and fern-allies have found their abode in the varied habitats of Western Ghats. 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. The pteridophytes tend to increase in number in the north-south direction in Western Ghats, obviously due to the more number of rainy months and higher altitudes with cooler climates, which prevail more towards the central and southern sectors. Thus whereas Maharashtra has 64 species of Pteridophytes, most of them confined to northern Western Ghats, (Manickam et al., 2003), Karnataka has about 174 species of pteridophytes, mostly growing in central Western Ghats (Rajagopal and Bhat, 1998) and Kerala and Tamil Nadu together, especially in a block south of Palghat gap account for 239 species (Manickam and Irudayaraj, 1992) (Table 1).

Table 1: Pteridophyte species distribution in relation to rainy months in Western Ghats

The Karnataka State, encompassing central Western Ghats, is a rich region in biodiversity due to its diversity of climatic conditions, soil and topographic variations. The different environmental regimes support their own characteristic set of plants and animals. Notable studies here began with listing of 75 species of ferns from North Canara (Uttara Kannada) district by Matchperson (1890). Later, in 1922, Blatter & Almeida included 90 species of ferns from Uttara Kannada district, then a part of Bombay Presidency, in their “Ferns of Bombay”. After a long lapse of time Alston (1945) gathered 4 species of Selaginella from the State contributing to his collection pool 58 species from India. Kammathy et al (1967) listed 25 species of ferns and fern-allies in their “Contribution towards a Flora of Biligirirangana Hills”. Razi & Rao (1971) published an artificial key to the Pteridophytes of Mysore city and its neighbouring areas in which they included 70 species of ferns and fern-allies spread over 41 genera. Bhaskar & Razi (1973) recorded 7 species of ferns and one species of Selaginella from aquatic and semi-aquatic habitats of Mysore district. Holttum (1976) included 10 members of Thelypteridaceae in the “Flora of Hassan District”. Yoganarsimhan et al (1981) described 12 species of ferns in their “Flora of Chikmagalur District”. However, the only in depth and comprehensive work on the pteridophytes of Karnataka was carried out by Rajagopal and Bhat (1998). Their work spanning a period from 1988-1995 culminated in the “Pteridophytic Flora of Karnataka State, India” published in 1998 listed 174 species. Ramachandra et al (2010) documented 54 species of pteridophytes from the Gundia river basin in Hassan district. The important pteridophytes hot-spots in Karnataka include Kemmangundi and Bababudan hills (Chikmagalur district), Bisle Ghat and adjoining areas (Hassan district), Agumbe Ghats (Shimoga district) and Gerusoppa Ghats, Kaiga and Castle Rock (Uttara Kannada district).