Sexual Selection and the Evolution of Song and Brain Structure in Acrocephalus Warblers

Abstract

Publisher Summary Acrocephalus warblers and their elaborate songs have proved to be rich and fertile ground, on which to test functional and evolutionary hypotheses. In particular, they have contributed in understanding the functions of song and the importance of song as a cue in female choice. In socially monogamous species, such as the sedge warbler, the female needs a good quality male to help raise the young successfully. This emphasized on selecting the male directly, and the long, complex songs function as a cue in female attraction. In polygamous species, such as the great reed warbler, resources are also important because the male may not help with feeding the young. Although females still use more complex male songs as a cue in mate choice, males have also developed short, simple songs for territorial defense. In the aquatic warbler, in which there is intense sperm competition, a special type of short song is used to repel rival males. Intra-sexual selection has led to the evolution of short, simple songs used in aggressive interactions with rival males, and intersexual selection by female choice has led to the longer, more complex songs used to attract females.