Allometry and Metabolic Scaling in Ecology


Body size affects the structure and function of all levels of biological organization. In ecological systems, body size strongly influences individuals (e.g. rates of individual growth, reproduction and mortality), populations (e.g. population growth rate, abundance and space use), communities (e.g. community abundance, food‐web structure and interspecific interactions) and ecosystems (e.g. flux, storage and turnover of materials and energy). This is because individual metabolic rate – the rate at which an organism takes up and utilizes energy and materials – is largely controlled by body size. Here we review how body‐size allometries at the individual level affect the structure and function of populations, communities and ecosystems. We use these results to identify and highlight exciting new applications of allometric theory in ecology.

Key concepts:

  • Body size sets an organism's metabolic rate and thereby controls its rates of growth, reproduction and mortality.

  • Body size is a key predictor of population growth rate, density and carrying capacity through its effects on individual‐level rates of birth, death and resource use.

  • Body size influences community structure through its effects on individual‐level resource demands, individual life histories and interspecific interactions.

  • Body size affects predator–prey dynamics and food‐web interactions partially through its effects on metabolic rate.

  • The contribution of biota to the cycling of energy and materials in ecosystems is affected by species’ size distributions, and by the flux, storage and turnover of energy and elements in individuals which, in turn, is controlled by metabolic rate.

  • Allometric models provide a baseline for understanding the structure and function of complex ecological systems, and a means to quantitatively link different levels of biological organization.

Keywords: allometry; body size; scaling; metabolic theory of ecology; energetics

Figure 1.

Schematic diagram illustrating allometric relationships with different exponents, b, and a constant normalization constant (yo=1) on both (a) arithmetic and (b) logarithmic scales.

Figure 2.

Allometries of life‐history variables: (a) temperature‐corrected, normalized development times (time to first heartbeat, time to hatching and generation time), where similar intercepts reflect the observation that the time to any specified developmental endpoint is similarly constrained by body mass (adapted from Gillooly et al. , copyright 2008 by The Royal Society), and (b) temperature‐corrected mortality rates (adapted from McCoy and Gillooly , with permission of Blackwell Publishing). See original publications for explanation of normalization and temperature correction.

Figure 3.

Allometries of population dynamics: (a) temperature‐corrected intrinsic rate of population increase, rmax (adapted from Savage et al. , Copyright 2004 by The University of Chicago) and (b) temperature‐corrected population density (adapted from Allen et al. ; used with permission from AAAS). See original references for explanation of temperature correction.

Figure 4.

Theoretically predicted allometric structuring of density, energy flux and biomass, (a) within a single trophic level and (b) in an idealized food‐web community with 104‐fold differences in body size between tropic levels (L1, L2 and L3) and a 10% efficiency of energy transfer from one trophic level to the next. Adapted from Brown and Gillooly , Copyright 2003 by The National Academy of Sciences of the USA.

Figure 5.

Allometries of ecosystem properties: (a) whole‐ecosystem xylem flux as a function of average plant mass (reprinted by permission from Enquist et al. , copyright 1998; and (b) biomass turnover in plant communities (adapted from Allen et al., , with permission of Wiley‐Blackwell).



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Further Reading

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Anderson‐Teixeira, Kristina J, Savage, Van M, Allen, Andrew P, and Gillooly, James F(Dec 2009) Allometry and Metabolic Scaling in Ecology. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0021222]