FEMALE PREFERENCE FOR FLY SONG - PLAYBACK EXPERIMENTS CONFIRM THE TARGETS OF SEXUAL SELECTION

The courtship song of Drosophila is thought to be involved in sexual s election and species recognition. Because of the mating system of flie s, however, directly demonstrating that song influences female prefere nce is difficult. The majority of previous studies have used an experi mental design that potentially confounds male and female reactions to song. In D. montana, correlational evidence has suggested that males t hat produce short sound pulses consisting of a high number of sound cy cles (i.e. a high carrier frequency) have a higher mating-success than other males. In this study, we played synthetic song that varied in p ulse length and carrier frequency to individual females in the laborat ory, both alone and in the presence of mute males. We scored female pr eference via an acceptance posture, 'wing spreading', which the female s of this species usually display prior to mounting by a male. Females responded to synthetic song in the absence of males. The presence of mute males significantly increased their overall responsiveness, but t he relative effectiveness of the songs did not change, eliminating mal e reaction to song as a possible confounding factor in the results. Th e interaction between pulse length and carrier frequency determined th e discrimination between song types, with females responding most read ily to song consisting of short pulses with a high carrier frequency. Thus, direct examination of female preferences supports the previous s tudies of male mating success, and confirms female song preference as a likely determinant of male mating success. (C) 1998 The Association for the Study Animal Behaviour.