Wild Orchids of Sharavathi River Basin and Parts of Uttara Kannada
G. R. Rao
Energy & Wetlands Research Group,
Center for Ecological Sciences,
Indian Institute of Science, Bangalore
Orchids, more than any other plants, exert a mysterious fascination for most people, and all the wild orchids of tropical regions are highly puzzling and peculiar. These graceful plants belong to family Orchidaceae being one of the largest families of flowering plants. This family is represented by more than 17,000 known wild species in 750 genera in the world and the present figure of the hybrids among these touches around 80,000 (Rao T A., 1998). The Orchidaceae contains more species than almost any other flowering plant family, being rivaled only by Compositae or Asteraceae. The family is cosmopolitan but with many more species in the tropics than in the temperate regions. It has a varied range of life forms, including both green terrestrial species such as are familiar in temperate regions, and in addition a large number of epiphytes of great range of size, common in the tropics. Some orchids like Vanilla are lianas and many species of all life forms, including the large lianas, are achlorophyllus and are often regarded as saprophytic. The smallest orchids, Cryptoanthemis slateri and Rhizanthella gardneri , are completely subterranean including their flower buds and have a fresh weight of few grams at most; the largest orchid is said to weigh over a ton (J L Harley, 1983). Apart from the popular and some time bizarre flowers with complex pollination mechanisms, the orchids are remarkable for two characters: firstly their seeds are small, the largest is about 14 m g, and within them the embryo is little differentiated: secondly they are all mycorrhizal, living throughout life in association with fungi.
Nearly 410 species of flowering plants have been reported as endangered in Western Ghats, out of which 235 species are endemic. Among the 924 wild species of Orchids listed from the present boundaries of India ranging in about 132 genera nearly 287 species distributed over 71 genera are endemic (Rao T A., 1998). The high endemism in orchids is perhaps because of certain physiological adaptive syndrome of the family bringing greater constrains on their existence, spread and replenishment in any particular area, viz.,
- Their existence in specific niches within the fragile ecosystem.
- Insect pollination in most of the species, particularly needing specific vectors to visit different species.
- Inability to achieve fertilization in maximum number of ovules for viable seeds due to the fact that each ovary of the orchid possesses millions of ovules.
- Presence of an unorganized embryo in the seed, also without any food storage and hence needing infection of a specific strain/race of mycorrhiza as a food supplier before germination.
- Suitability of the particular niche where the seed syndrome for the specific establishment has not been examined.
- Absence of corridors for orchid seedlings/propagules to pass through similar niches for establishment and dispersal.