REPRODUCTIVE ECOLOGY OF THE BOREAL RIPARIAN GUILD OF DROSOPHILA

The reproductive ecology of four sympatric Drosophila virilis group species (Diptera: Drosophilidae) was studied in the field to trace the factors maintaining species isolation. There was a high probability of meeting a heterospecific individual belonging to the same species group on the basis of adult spatial occurrence. Direct field observations revealed that the males court also females of the foreign species, but interspecific courtships do not lead to mating. The main mating period among these species lasted only several weeks, and the timing of mating periods differed markedly in the three most common species. Reproductive character displacement between species may explain the observed differences in the timing of the mating periods, but they could have arisen in the context of other selective pressures than the prevention of interspecific courtships and matings.