Bite performance and morphology in a population of Darwin's finches: implications for the evolution of beak shape

Authors

  • A. HERREL,

    Corresponding author
    1. Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610 Antwerpen, Belgium,
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  • J. PODOS,

    1. Department of Biology, University of Massachusetts Amherst, Amherst MA 01003, USA,
    2. Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts Amherst, Amherst MA 01003 USA, and
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  • S. K. HUBER,

    1. Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts Amherst, Amherst MA 01003 USA, and
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  • A. P. HENDRY

    1. Redpath Museum and Department of Biology, McGill University, 859 Sherbrooke St. W., Montréal, Québec, Canada H3A 2K6
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†Author to whom correspondence should be addressed. E-mail: aherrel@uia.ua.ac.be

Summary

  • 1Previous studies of the Medium Ground Finch, Geospiza fortis, have documented that selection is most severe under drought conditions, which generally favour beaks that are comparatively deep and narrow. Deep beaks are presumed to enhance a bird's ability to crack hard seeds, and narrow beaks have been proposed to enhance a bird's efficiency in manipulating seeds.
  • 2In the present study, we make the first direct measurements of bite force in Darwin's finches. We used 147 G. fortis from Isla Santa Cruz, Galápagos, to document the influence of beak, head and body dimensions on bite force.
  • 3Among the various beak dimensions, depth, width and shape were all significant predictors of bite force. Among the various head dimensions, width was the best predictor of bite force. Generally low predictive values of multiple regression models including all morphological variables, as well as positive allometric scaling of bite force on head width, suggest an important additional role for variation in muscle architecture or jaw biomechanics in bite force generation.

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