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Why are metabolic scaling exponents so controversial? Quantifying variance and testing hypotheses

Authors

  • Nick J. B. Isaac,

    Corresponding author
    1. Institute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, UK
    2. NERC Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxon OX10 8BB, UK
      Correspondence: E-mail:njbisaac@gmail.com
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  • Chris Carbone

    1. Institute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, UK
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Correspondence: E-mail:njbisaac@gmail.com

Abstract

Ecology Letters (2010) 13: 728–735

Abstract

The metabolic theory of ecology links physiology with ecology, and successfully predicts many allometric scaling relationships. In recent years, proponents and critics of metabolic theory have debated vigorously about the scaling of metabolic rate. We show that the controversy arose, in part, because researchers examined the mean exponent separately from the variance. We estimate both quantities simultaneously using linear mixed-effects models and data from 1242 animal species. Metabolic rate scaling converges on the predicted value of 3/4 but is highly heterogeneous: 50% of orders lie outside the range 0.68–0.82. These findings are robust to several forms of statistical uncertainty. We then test competing hypotheses about the variation. Metabolic theory is currently unable to explain differences in scaling among orders, but the patterns are not consistent with competing explanations either. We conclude that current theories are inadequate to explain the full range of metabolic scaling patterns observed in nature.

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