Data from: Multi-modal signal evolution in birds: re-examining a standard proxy for sexual selection

Sexual selection is proposed to be an important driver of speciation and
phenotypic diversification in animal systems. However, previous
phylogenetic tests have produced conflicting results, perhaps because they
have focused on a single signalling modality (visual ornaments), whereas
sexual selection may act on alternative signalling modalities (e.g.
acoustic ornaments). Here we compile phenotypic data from 259 avian sister
species pairs to assess the relationship between visible plumage
dichromatism—a standard index of sexual selection in birds—and
macroevolutionary divergence in the other major avian signalling modality:
song. We find evidence for a strong negative relationship between the
degree of plumage dichromatism and divergence in song traits, which
remains significant even when accounting for other key factors, including
habitat type, ecological divergence and interspecific interactions. This
negative relationship is opposite to the pattern expected by a
straightforward interpretation of the sexual selection-diversification
hypothesis, whereby higher levels of dichromatism indicating strong sexual
selection should be related to greater levels of mating signal divergence
regardless of signalling modality. Our findings imply a ‘trade-off’
between the elaboration of visual ornaments and the diversification of
acoustic mating signals, and suggest that the effects of sexual selection
on diversification can only be determined by considering multiple
alternative signalling modalities.