The evolution of courtship display repertoire size in the dabbling ducks (Anatini)

Many animals possess multiple ornaments or behaviours that seem to have evo lved via sexual selection. A complete understanding of sexual selection req uires an explanation for such multiple traits. The dabbling ducks (Tribe: A natini) exhibit considerable variation among species in the number of displ ays in the male courtship repertoire. I tested five hypotheses concerning t he evolution of the variation in display repertoire size of dabbling ducks: (1) species recognition, (2) courtship habitat, (3) sexual selection inten sity, (4) display media tradeoff and (5) time constraints on pair formation . I tested these hypotheses, using an explicit phylogenetic hypothesis deve loped from DNA sequences for the dabbling ducks, with two types of statisti cal comparative methods (discrete and continuous character). The variation observed in male courtship display repertoire size in dabbling ducks was co nsistent with the courtship habitat and sexual selection intensity hypothes es. Specifically, the size of the display repertoire was larger in species that exhibit courtship exclusively on water and larger in species with dimo rphic plumage. These results suggest that ecological (habitat) as well as s ocial (sexual selection) factors may be important in driving the evolution of displays in the dabbling ducks.