Differentiation of dialects and courtship strategies in allopatric populations of Drosophila teissieri.

Intra-specific differentiation has been investigated between two geographically isolated populations of D. teissieri, one from Brazzaville (Congo) and the other from Silinda (Zimbabwe). Courtship songs were analyzed on 23 parameters. In addition, certain parameters related to sexual activity (five) and wing morphology (five) were also examined. As in other Drosophilidae, there are two types of courtship songs resulting from wing vibration: the love song, and the sine song. Love songs from Brazzaville are longer than those from Silinda (334ms vs. 216) with a tendency to smaller and more regular inter-pulse intervals (24.56ms vs. 25.5). The sine songs (SS) are about six times longer than the love songs in each population, with an adaptation of their duration according to the receptivity of the female in Brazzaville. All the LS temporal parameters, except the interpulse interval mean, are significantly different between the two populations. The Brazzaville flies show a greater acoustic activity and have higher mating success than the Silinda ones (53.3% vs. 27.7%). Their wings are slightly shorter and wider than those from Silinda. The role of acoustic parameters, sexual activity and wing physical constraints are discussed in the perspective of incipient speciation.