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

Christopher Cooney, Hannah MacGregor, Nathalie Seddon, Joseph Tobias

Research output: Contribution to journalArticle (Academic Journal)

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Abstract

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.
Original languageEnglish
Article number20181557
Number of pages8
JournalProceedings of the Royal Society of London B: Biological Sciences
Volume285
Issue number1889
Early online date17 Oct 2018
DOIs
Publication statusPublished - 24 Oct 2018

Keywords

  • dichromatism
  • divergence
  • plumage
  • sexual selection
  • song
  • trade-off

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