Effects of age and experience on mating activity in the sibling species Drosophila pavani and Drosophila gaucha.

The effects of age and experience on sexual activity and on intra- and interspecific discrimination were studied in two sibling species of the mesophragmatica group, Drosophila pavani and Drosophila gaucha. Sexual activity of a total of 2970 individual couples of the same or of both species was observed at two ages: 10 days, ("young inexperienced") and 18-20 days ("old," either "inexperienced" or "experienced," if either the male or the female had copulated previously). In the 1186 (39.97%) pairs that mated, the latency to copula and duration of copula were registered. Age has a different effect in both species: "young" Drosophila pavani and "old" Drosophila gaucha females are less receptive to males of either species of the corresponding age. The receptivity of females is also reflected in heterospecific matings, as Drosophila gaucha males increase their mating activity with age. In both species, female receptivity decreases with experience, whereas mating activity of males increases with experience, especially that of Drosophila gaucha toward heterospecific females. Drosophila pavani females take longer to mate than those of Drosophila gaucha. In both species "old" males tend to mate faster, whereas experience increases the latency to mating in females and decreases it in males. Both species differ significantly in the duration of copula. It is longer in Drosophila pavani than in Drosophila gaucha and is determined mainly by the male. The duration of copula increases with age, especially in Drosophila pavani females, whereas it is reduced in males of the same species.