The reproductive role hypothesis explains trophic morphology dimorphism in the northern map turtle

Authors

  • G. Bulté,

    Corresponding author
    1. Department of Biology, University of Ottawa, 30 Marie-Curie, Ottawa, ON, Canada, K1N 6N5; and
      *Correspondence author. E-mail: gbult087@uottawa.ca
    Search for more papers by this author
  • D. J. Irschick,

    1. Department of Biology and Organismic and Evolutionary Biology Program, University of Massachusetts Amherst, 221 Morrill Science Center, Amherst, MA 01003 USA
    Search for more papers by this author
  • G. Blouin-Demers

    1. Department of Biology, University of Ottawa, 30 Marie-Curie, Ottawa, ON, Canada, K1N 6N5; and
    Search for more papers by this author

*Correspondence author. E-mail: gbult087@uottawa.ca

Summary

  • 1Sexually dimorphic traits often reflect factors limiting the reproductive success of animals. Thus, most sexually dimorphic traits can be directly linked to the reproductive role of each sex. Sexual dimorphism in trophic structures (e.g. beak, jaws, teeth), however, often lacks a direct link to reproduction.
  • 2Trophic structures can be linked indirectly to reproductive allocation via energy acquisition. The reproductive role hypothesis (also known as the dimorphic niche hypothesis) posits such an indirect link, but has received heretofore little direct empirical support. We tested this hypothesis in a molluscivorous turtle exhibiting marked female-biased trophic morphology dimorphism.
  • 3Bite force analysis showed that females have stronger jaws than males and dietary analysis revealed that females ingest snails closer to their maximum biting capacity than males. Body condition of both sexes and reproductive output of females increased with relative head width, indicating that fitness is tightly linked to head size and bite force.
  • 4Our study provides strong evidence that reproductive role contributes to sexual dimorphism in trophic morphology. Our findings should apply to any animal in which energy intake is limited by trophic morphology.

Ancillary