Introduction

Pteridophytes (ferns and fern-allies) are the most primitive vascular plants that appeared on the Earth, in the mid-Paleozoic era during the Silurian period which began 438 million years ago. They are the earliest of the plants ever evolved on the earth heralding the presence of a well developed vascular system -xylem for water and phloem for food transport respectively and hence, are referred as ‘vascular cryptogams’. The arrival of pteridophytes, withspecialized water and food conducting tissues,heralded an era of greater colonization in terrestrial ecosystems, to an extent that many of them could attain great heights like the flowering trees. After successfully establishing themselves as land plants, a very rapid rate of evolution was stimulated and witnessed among them with which they dominated most of the forests on earth’s surface by the approach of carboniferous period. With the passage of time, especially with the evolution and dominance of the flowering plants, beginning in the late Cretaceous, the decline of the pteridophytes began. Nevertheless, this interesting group of plants, bridging the non-vascular cryptogams with the seed plants, higher in the evolutionary hierarchy, continues to occupy numerous niches on the land and in marshes and swamps and even in water bodies (Dudani et al., 2011).

India has a rich and varied pteridophytic flora due to its Gondwanaland origin, its drift from south of the Equator towards Eurasia far north, carrying the progenitors of today’s pteridophytes from Australia, Africa, Madagascar etc. as well as probable endemics of its own. The rise of the Himalayas along the India-Eurasia merger line created diversified topography and varied climatic conditions ranging from warm and humid sea shores to arid deserts to elevations experiencing arctic cold, creating numerous micro-climates congenial for growth of ferns and fern allies, almost unparalleled anywhere on the Earth.  Moreover India’s strategic geographical position would have facilitated migration of species, including several pteridophytes from Eurasia and South-east Asia and vice-versa, a notable factor that would have reduced endemism among the fern community.  Today, among the vascular plants, pteridophytes form a major part next only to the angiosperms in India. Of the 12, 000 or so pteridophyte species enumerated in the world, around 1000 species from 70 families and 192 genera occur in India. The major centers for pteridophytes diversity are Eastern and Western Himalayas, Western Ghats, Eastern Ghats, Central India and Andaman and Nicobar Islands.

The Western Ghats 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 over 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), covering a geographical area of about 160,000 km2, is interrupted only by a 30 km break in Kerala, the Palghat Gap (Radhakrishna, 2001). 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 mainly the districts of Uttara Kannada, Shimoga, Chikmagalur, Hassan, Kodagu, Udupi and Dakshina Kannada, constituting the Central Western Ghats, a region endowed with a wide range of vegetation types and extremely rich biodiversity (Ramachandra et al., 2012).

The presence of perennial streams and rivers, evergreen forests, grasslands and high altitude sholas and many other habitats of this mountain chain harbor almost 320 species of ferns and fern-allies. The pteridophytes tend to increase in number in the north-south direction of Western Ghats, obviously due to the more number of rainy months and higher altitudes with cooler climates. 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 alone account for 239 species (Manickam and Irudayaraj, 1992).

There have been some notable studies on the pteridophytes of central Western Ghats in Karnataka with the earliest record of 75 ferns species from North Canara district (Matchperson, 1890). After a gap of more than three decades, Blatter and Almeida (1922) included 90 species of ferns from North Canara district in their work ‘Ferns of Bombay’. Subsequent studies on pteridophytes of Karnataka included collection of four species of Selaginella from the state by Alston (1945); listing of 25 species of pteridophytes by Kammathy et al (1967); preparation of an artificial key for the 70 species of pteridophytes recorded from Mysore city and its neighboring areas; inclusion of 10 species of fern family Thelypteridaceae in ‘Flora of Hassan District’ by Holttum (1976) and inclusion of 12 species of fern by Yoganarasimhan et al (1981) in ‘Flora of Chikmagalur District. After a significant time gap, there has been a surge in various research aspects of pteridophytes of central Western Ghats. Some of the recent studies on ferns and fern-allies include the record of 23 species of pteridophytes in Madhuguni state forest of central Western Ghats by Deepa et al (2011); enumeration of 22 species of pteridophytes from Agumbe forest of central Western Ghats (Nataraja et al, 2011); survey and record of 21 species of pteridophytes in the Yana sacred forests of central Western Ghats by Dudani et al (2013) and record of 38 taxa of pteridophytes from Kemmangundi forest of Karnataka by Deepa et al (2013). As it is evident from the available literatures, there is still a serious derth of information pertaining to the pteridophyte diversity of many important biodiversity rich areas of Karnataka. Hence, this study was taken up with the aim of exploring the pteridophytic diversity as a part of an ecological study carried out by our multi-disciplinary team during 2010-11 in the Sakleshpur taluk of Hassan district.