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Publication - Dr Hannah MacGregor

    Multi-modal signal evolution in birds

    re-examining a standard proxy for sexual selection

    Citation

    Cooney, C, MacGregor, H, Seddon, N & Tobias, J, 2018, ‘Multi-modal signal evolution in birds: re-examining a standard proxy for sexual selection’. Proceedings of the Royal Society of London B: Biological Sciences, vol 285.

    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.

    Full details in the University publications repository