Evolutionary maintenance of sexual dimorphism in head size in the lizard Zootoca vivipara: a test of two hypotheses


  • Lumír Gvozdík,

    Corresponding author
    1. Department of Population Biology, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Studenec 122, CZ-67502 Konesín, Czech Republic
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  • Raoul Van Damme

    1. Laboratory of Functional Morphology, Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
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*L. Gvozdík E-mail: gvozdik@brno.cas.cz


Zootoca vivipara is a small lizard that shows sexual dimorphism in head size. Males have larger heads than females of the same body size. By observing matings and aggressive interactions between males in the laboratory, we investigated whether this sexual dimorphism could be the result of intra- and/or intersexual selection. Winners of male–male interactions had larger heads than losers. During mating attempts, males with larger heads succeeded in grasping a female faster than males with smaller heads. It follows that head size in Z. vivipara may affect male reproductive success both through intrasexual competition (fighting ability) and through intersexual selection (grasping ability). This suggests that sexual selection may be the cause for the sexual dimorphism in head size in this species.