Contribution By Males To Intraspecific Variation Of The Light Dependency Of Mating In The Drosophila Melanogaster Species Subgroup

Seven species of the Drosophila melanogaster species subgroup were compared for mating success under different light conditions (light or dark). All species except D. melanogaster showed a significantly lower frequency of mating success in the dark than in light in a one-hour mating experiment. Among the six light-dependent species, D. sechellia showed the lowest frequency in the dark and D. simulans showed the highest in the dark. They were chosen for further intraspecific comparisons using four strains respectively. A substantial difference in the mating frequency in the dark was again found among the four strains in both D. sechellia and D. simulans, respectively. In these two species reciprocal mating experiments were then performed between the two strains showing the highest and the lowest frequency in the dark. In both species males from the strains with a low mating frequency also showed low scores with the females from the strain that showed a high score. It is therefore shown that males predominantly contribute to the low frequency of mating success in the dark while females appear to make a negligible contribution to the light dependency of mating. The male flies in both D. sechellia and D. simulans showing high mating frequency did not always show a high locomotor level under light or in the dark. We conclude that the decrease of the mating frequency in the dark is caused by the light-dependent mechanism of male-specific sexual behavior rather than by a mechanism associated with general activity.