PARALLEL SELECTION OF ETHANOL AND ACETIC-ACID TOLERANCE IN DROSOPHILA-MELANOGASTER POPULATIONS FROM INDIA

Nine Indian geographical populations of Drosophila melanogaster, collected along the 20 degrees N latitudinal range, revealed a significant clinal variation at the alcohol dehydrogenase (Adh) locus, Adh(F) allelic frequency increasing significantly with latitude (0.036 +/- 0.004 for 1 degrees latitude genetic divergence F-ST = 0.25). Patterns of ethanol and acetic-acid tolerance in adult individuals revealed significant genetic divergence. Parallel patterns of latitudinal ethanol tolerance (10 to 15%) and acetic-acid tolerance (3.7 to 13.2%) were observed in adult individuals from the 9 geographical populations. Thus, the northern and southern populations revealed divergence in the patterns of resource utilisation. The parallel latitudinal genetic divergence at the Adh locus and for ethanol and acetic-acid tolerance in Indian populations of Drosophila melanogaster could be explained by balancing natural selection varying spatially along the north-south axis of the Indian subcontinent.