It is all in the head: morphological basis for differences in bite force among colour morphs of the Dalmatian wall lizard

Authors

  • KATLEEN HUYGHE,

    Corresponding author
    1. Laboratory for Functional Morphology, Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium
      E-mail: katleen.huyghe@ua.ac.be
    Search for more papers by this author
  • ANTHONY HERREL,

    1. Laboratory for Functional Morphology, Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium
    2. Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
    Search for more papers by this author
  • DOMINIQUE ADRIAENS,

    1. Evolutionary Morphology of Vertebrates, Ghent University, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium
    Search for more papers by this author
  • ZORAN TADIĆ,

    1. Department of Animal Physiology, University of Zagreb, Rooseveltov trg 6, 10000 Zagreb, Croatia
    Search for more papers by this author
  • RAOUL VAN DAMME

    1. Laboratory for Functional Morphology, Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium
    Search for more papers by this author

E-mail: katleen.huyghe@ua.ac.be

Abstract

Males of the lizard Podarcis melisellensis occur in three distinct colours that differ in bite performance, with orange males biting harder than white or yellow ones. Differences in bite force among colour morphs are best explained by differences in head height, suggesting underlying variation in cranial shape and/or the size of the jaw adductors. To explore this issue further, we examined variation in cranial shape, using geometric morphometric techniques. Additionally, we quantified differences in jaw adductor muscle mass. No significant differences in size corrected head shape were found, although some shape trends could be detected between the colour morphs. Orange males have relatively larger jaw adductors than yellow males. Not only the mass of the external jaw adductors, but also that of the internal jaw adductors was greater for the orange morph. Data for other cranial muscles not related to biting suggest that this is not the consequence of an overall increase in robustness in orange individuals. These results suggest that differences in bite performance among morphs are caused specifically by an increase in the mass of the jaw adductor, which may be induced by differences in circulating hormone levels. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 13–22.

Ancillary