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Functional differentiation of African grazing ruminants: an example of specialized adaptations to very small changes in diet

Authors

  • DARYL CODRON,

    Corresponding author
    1. School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa
    2. Florisbad Quaternary Research, National Museum, Bloemfontein 9300, South Africa
      E-mail: codron@ukzn.ac.za
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  • JAMES S. BRINK,

    1. Florisbad Quaternary Research, National Museum, Bloemfontein 9300, South Africa
    2. Centre for Environmental Management, Faculty of Natural and Agricultural Science, University of the Free State, Bloemfontein, 9300, South Africa
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  • LLOYD ROSSOUW,

    1. Florisbad Quaternary Research, National Museum, Bloemfontein 9300, South Africa
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  • MARCUS CLAUSS,

    1. Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, 8057, Switzerland
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  • JACQUI CODRON,

    1. Department of Archaeology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa
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  • JULIA A. LEE-THORP,

    1. Department of Archaeological Sciences, Bradford University, Bradford BD7 1DP, UK
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  • MATT SPONHEIMER

    1. Department of Anthropology, University of Colorado at Boulder, Boulder, CO 80309, South Africa
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E-mail: codron@ukzn.ac.za

Abstract

We assess whether interspecific differences in craniodental morphology within a single ruminant feeding guild, the grazers, represent anatomical adaptations to subtle differences in diet. Differences in craniodental anatomy follow a distinct taxonomic pattern that is paralleled by dietary niche differentiation recorded in species' stable carbon (δ13C) and nitrogen isotope (δ15N) compositions, strongly supporting a hypothesis for functional divergence within the grazers. We propose that the evolutionary origin of grazers were multifold; at least two and up to four different types of grazing can be discerned within the 11 taxa studied here alone. However, correspondence between craniodental adaptations and isotopic differences across species are not found when only δ13C data are considered (i.e. morphological differences do not reflect varying proportions of C3 browse to C4 grass consumed). This implies that alternate anatomical adaptations to grazing are not related to differences between variable (part-time browsing) and obligate grazers, as previously predicted. Rather, anatomical differences correlate strongly with changes in δ15N, which we infer to reflect functional responses to changes in diet quality associated with the degree of feeding selectivity and short-, medium-, or tall-grass grazing. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 755–764.

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