Sexual isolation between Drosophila melanogaster females and D. simulans males. Male mating propensities versus success in hybridization.

Genetic variation has been found in males of a D. simulans population for their eagerness to hybridize with D. melanogaster females. In a search for traits involved in this hybridization, males of D. simulans were tested for mating speed and sexual vigour. Between-male differences were detected in both sexual traits, but no relationship was noticed between them, nor with the frequency of hybridization. Thus male mating propensities appear to be unrelated to the breakdown of sexual isolation between these sibling species.