MATING PROPENSITY OF INDIAN DROSOPHILA-MELANOGASTER POPULATIONS WITH DROSOPHILA-SIMULANS - A NONADAPTIVE LATITUDINAL CLINE

Crosses were investigated between a single strain of Drosophila simula ns and 28 natural Indian populations of D. melanogaster. In each case, a mass culture and 10 isofemale lines of D. melanogaster were studied . Crosses were much easier between D. melanogaster females and D. simu lans males than in the reciprocal case. Also, hybrid offspring were ea sier to obtain by using D. melanogaster flies (either males or females ) from isofemale lines than from mass cultures. Finally, the crossabil ity, estimated by progeny production, showed a clear-cut latitudinal d ine: hybrids were easier to obtain with D. melanogaster populations fr om higher latitudes. As D. simulans does not occur in India, this dine does not reflect an evolutionary interaction between the two sibling species.