Female common lizards (Lacerta vivipara) do not adjust their sex-biased investment in relation to the adult sex ratio

Authors

  • J.-F. LE GALLIARD,

    1. Laboratoire Fonctionnement et Evolution des Systèmes Ecologiques, Université Pierre et Marie Curie, Paris
    2. Centre for Ecological and Evolutionary Synthesis, University of Oslo, Blindern, Norway
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      These authors contributed equally to this work

  • P. S. FITZE,

    1. Laboratoire Fonctionnement et Evolution des Systèmes Ecologiques, Université Pierre et Marie Curie, Paris
    2. Department of Zoology, University of Cambridge, Downing Street, Cambridge, UK
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      These authors contributed equally to this work

  • J. COTE,

    1. Laboratoire Fonctionnement et Evolution des Systèmes Ecologiques, Université Pierre et Marie Curie, Paris
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  • M. MASSOT,

    1. Laboratoire Fonctionnement et Evolution des Systèmes Ecologiques, Université Pierre et Marie Curie, Paris
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  • J. CLOBERT

    1. Laboratoire Fonctionnement et Evolution des Systèmes Ecologiques, Université Pierre et Marie Curie, Paris
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Jean-François Le Galliard, Centre for Ecological and Evolutionary Synthesis, University of Oslo, P.O. Box 1050, Blindern, Oslo NO-0316, Norway.
Tel: +47 22 85 46 08; fax: +47 22 85 46 05;
e-mail: j.f.l.galliard@bio.uio.no

Abstract

Sex allocation theory predicts that facultative maternal investment in the rare sex should be favoured by natural selection when breeders experience predictable variation in adult sex ratios (ASRs). We found significant spatial and predictable interannual changes in local ASRs within a natural population of the common lizard where the mean ASR is female-biased, thus validating the key assumptions of adaptive sex ratio models. We tested for facultative maternal investment in the rare sex during and after an experimental perturbation of the ASR by creating populations with female-biased or male-biased ASR. Mothers did not adjust their clutch sex ratio during or after the ASR perturbation, but produced sons with a higher body condition in male-biased populations. However, this differential sex allocation did not result in growth or survival differences in offspring. Our results thus contradict the predictions of adaptive models and challenge the idea that facultative investment in the rare sex might be a mechanism regulating the population sex ratio.

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