Individual-level diet variation in four species of Brazilian frogs

Authors

  • M. S. Araújo,

    Corresponding author
    1. Departamento de Parasitologia, Instituto de Biologia, Universidade Estadual de Campinas, Caixa Postal 6109, 13083-970, Campinas, SP, Brazil
      *Correspondence author. E-mail: msaraujo@gmail.com
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    • Present address: Integrative Biology, University of Texas at Austin, 1 University Station C0930, Austin, TX 78712, USA

  • D. I. Bolnick,

    1. Integrative Biology, University of Texas at Austin, 1 University Station C0930, Austin, TX 78712, USA
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  • L. A. Martinelli,

    1. Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Av. Centenário, 303, 13416-000, Piracicaba, SP, Brazil
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  • A. A. Giaretta,

    1. Laboratório de Ecologia e Sistemática de Anuros Neotropicais, Instituto de Biologia, Universidade Federal de Uberlândia, 38400-902, Uberlândia, MG, Brazil
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  • S. F. Dos Reis

    1. Departamento de Parasitologia, Instituto de Biologia, Universidade Estadual de Campinas, Caixa Postal 6109, 13083-970, Campinas, SP, Brazil
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*Correspondence author. E-mail: msaraujo@gmail.com

Summary

  • 1Many natural populations exploiting a wide range of resources are actually composed of relatively specialized individuals.
  • 2This interindividual variation is thought to be a consequence of the invasion of ‘empty’ niches in depauperate communities, generally in temperate regions. If individual niches are constrained by functional trade-offs, the expansion of the population niche is only achieved by an increase in interindividual variation, consistent with the ‘niche variation hypothesis’.
  • 3According to this hypothesis, we should not expect interindividual variation in species belonging to highly diverse, packed communities.
  • 4In the present study, we measured the degree of interindividual diet variation in four species of frogs of the highly diverse Brazilian Cerrado, using both gut contents and δ13C stable isotopes.
  • 5We found evidence of significant diet variation in the four species, indicating that this phenomenon is not restricted to depauperate communities in temperate regions.
  • 6The lack of correlations between the frogs’ morphology and diet indicate that trade-offs do not depend on the morphological characters measured here and are probably not biomechanical. The nature of the trade-offs remains unknown, but are likely to be cognitive or physiological.
  • 7Finally, we found a positive correlation between the population niche width and the degree of diet variation, but a null model showed that this correlation can be generated by individuals sampling randomly from a common set of resources. Therefore, albeit consistent with, our results cannot be taken as evidence in favour of the niche variation hypothesis.

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