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

Nine Indian geographical populations of Drosophila melanogaster, colle cted along the 20 degrees N latitudinal range, revealed a significant clinal variation at the alcohol dehydrogenase (Adh) locus, Adh(F) alle lic frequency increasing significantly with latitude (0.036 +/- 0.004 for 1 degrees latitude genetic divergence F-ST = 0.25). Patterns of et hanol and acetic-acid tolerance in adult individuals revealed signific ant genetic divergence. Parallel patterns of latitudinal ethanol toler ance (10 to 15%) and acetic-acid tolerance (3.7 to 13.2%) were observe d 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 a t the Adh locus and for ethanol and acetic-acid tolerance in Indian po pulations of Drosophila melanogaster could be explained by balancing n atural selection varying spatially along the north-south axis of the I ndian subcontinent.