PARALLEL ADAPTATION TO ALCOHOLIC FERMENTATION IN ZAPRIONUS-INDIANUS AND DROSOPHILA-MELANOGASTER POPULATIONS

Eight Indian geographical populations of D. melanogaster and Z. indian us collected along 20 degrees N latitudinal range, revealed significan t Adh clinal variation, i.e., 3% and 1% for 1 degrees latitude in D. m elanogaster and Z. indianus, respectively. D. melanogaster populations could utilize 9.5 to 15.0 percent ethanol while Z. indianus populatio ns utilized 3.75 to 8.5 percent ethanol. The parallel patterns of inte rspecific divergence of ethanol tolerance level are compatible with th eir natural habitats, i.e., Z. indianus mainly utilized fermented orga nic matter and fruits in the wild while D. melanogaster exploits man m ade highly ethanol rich sources indoors. The present observations sugg est that Z. indianus revealed an adaptive characteristic for ethanol u tilization mainly while D. melanogaster populations have depicted both ethanol utilization as well as ethanol detoxification. The observed l atitudinal variation of Adh(F) frequency and ethanol tolerance in thes e two drosophilids could be maintained by balancing natural selection varying spatially along the north-south axis of the Indian sub-contine nt.