Forty years of solitude: Using laboratory lines of D. melanogaster to study behavioral isolation

Abstract

Population genetic models of speciation show that the initial population divergence can be very rapid when sexual signals are involved, and that speciation through sexual selection has a high probability compared to speciation through viability selection. The models also suggest that the exact nature of the changes in a signal system can be arbitrary. This raises empirical questions of whether behavioral divergence can be detected sooner than postzygotic isolation, and whether, in a multimodal signal system, certain signals are more likely to diverge than others. The early stages of behavioral isolation are being investigated by using stocks of D. melanogaster that have been in captivity for 40–50 years. Two lines that were part of a 1950s study of DDT resistance have begun to evolve behavioral isolation; however, postzygotic isolation is not detectable. The courtship signals of recently diverged populations can be compared to published reports of behavioral isolation between populations of D. melanogaster and between D. melanogaster and its close relative to learn whether signal divergence always follows the same trajectory.