Moving to mate: the evolution of separate and combined sexes in multicellular organisms

Authors

  • S. M. EPPLEY,

    1. Department of Biology, Portland State University, Portland, OR, USA
    2. School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
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  • L. K. JESSON

    1. School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
    2. Department of Biology, University of New Brunswick, Fredericton, New Brunswick Canada
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S. M. Eppley, Department of Biology, Portland State University, PO Box 751, Portland, OR 97207-0751, USA.
Tel.: +1 503 725 8986; fax: +1 503 725 3888;
e-mail: eppley@pdx.edu

Abstract

Which conditions favour the evolution of hermaphroditism or separate sexes? One classical hypothesis states that an organism’s mode of locomotion (if any) when searching for a mate should influence breeding system evolution. We used published phylogenies to reconstruct evolutionary changes in adult mate-search efficiency and breeding systems among multicellular organisms. Employing maximum-likelihood analyses, we found that changes in adult mate-search efficiency are significantly correlated with changes in breeding system, and this result is robust to uncertainties in the phylogenies. These data provide the first statistical support, across a broad range of taxa, for the hypothesis that breeding systems and mate-search efficiency did not evolve independently. We discuss our results in context with other causal factors, such as inbreeding avoidance and sexual specialization, likely to affect breeding system evolution.

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