Abstract

Post monsoon studies were conducted to analyze the altitudinal variation in a population ofDrosophila (Diptera: Drosophilidae) in Brahmagiri Wildlife Sanctuary belonging to the Western Ghats of Coorg district, Karnataka State, India. A total of 4636 Drosophila flies belonging to 8 species of 3 subgenera were collected at altitudes of 800, 900 and 1000 m. The subgenusSophophora was predominant with 5 different species, subgenus Drosophila with 2 different species and the subgenus Scaptodrosophila was least represented with only a single species. The population density varied in the above three altitudes and highest density was found at 800 m, then the density reduced at 900 m (380 flies) and once again the density increased at 1000 m. This shows that Drosophila community is affected by elevation. The diversity of theDrosophila community was also assessed by applying the Simpson and Berger-Parker indices. At 800 m, the Simpson Index was low at 0.37 and the Berger-Parker index was high at 0.47, 900 m. The distributional pattern of a species or related group of species was uneven in space and time. Drosophila kikkawai, Drosophila takahashii, Drosophila immigrans and Drosophila nigrawere found in all the three altitudes suggesting that these species are dominant in this region.

Key words: Drosophila, Brahmagiri Wildlife Sanctuary, Drosophila kikkawai, Drosophila takahashii, Drosophila immigrans, Drosophila nigra.