The role of courtship song in sexual selection and species recognition by female Drosophila melanogaster

Male fruit flies, Drosophila melanogaster, produce a complex courtship display, which females may use to identify conspecifics and to aid in choosing a high-quality mate. Courtship song, consisting of sine and pulse elements, is an important acoustic component of this display. Whereas characteristics that differ between species have been identified, the signals used for intraspecific mate choice remain unknown, as does the function of sine song. To investigate further the role of pulse and sine song, we varied characteristics of artificial and edited songs and played them to groups of flies to determine whether sine or pulse song parameters contribute to female mate choice. Playing artificial songs did not substantially change the amount of male courtship behaviour. Sine song in any proportion had no effect on female mating propensity, nor was mating affected by sine-song frequency. The amount of pulse song offered positively increased mating, up to a threshold, without regard to the structure of the song, pulse carrier frequency, or interpulse interval. These results indicate that females use pulse song, not sine song, for both species identification and intraspecific mate choice. Males may continue to produce sine song as a relic, as a by-product of a physiological process or because it is inextricably linked to a mate-choice signal in a different modality. The role of song memory is discussed briefly. (C) 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.