Metabolic Scaling Theory

by

Chuck Price

• LAST REVIEWED: 26 August 2014
• LAST MODIFIED: 26 August 2014
• DOI: 10.1093/obo/9780199830060-0101

Introduction

Body size is among the most influential variables one could measure in attempting to understand interspecific variability in metabolic requirements. Metabolism, in turn, represents the rate at which an organism exchanges and transforms resources from its environment and thus has broad implications for understanding the flow and transformation of energy and materials at many levels of biological organization. A longstanding question in the study of body size and metabolism has been: How does metabolic rate change with organism size? Change in organism size could be based on different measures, such as length, surface area, or, most commonly, mass. The change in size is then a change in scale and, in the language of practitioners, the question becomes: How does metabolic rate “scale” with size? The study of how changes in size influence other organism traits is known as allometry. It is sometimes referred to as “biological scaling,” which may include questions at many other levels of organization above and below the level of the individual.

General Overviews

The metabolic theory of ecology (MTE), which is also known as metabolic scaling theory (MST), is a collection of interrelated theories and empirical observations that attempts to forge mechanistic links between many different levels of organization in biology and ecology, from organelles to ecosystems. The broader theory invokes the central roles of organism size, temperature, and metabolism in determining numerous patterns within and across individuals, species, and clades. The foundation of MTE rests on the fractal branching model of West, et al. 2000 (WBE); however, many predictions do not rely directly on the details of the model and require only a power law relationship among mass, temperature, and metabolism. A complete treatment of the history and current state of metabolic ecology would require a considerable effort. This article highlights the mechanistic underpinnings and causal links between certain key concepts and discusses some of the more active areas in the field. Edited volumes—Brown and West 2000 or Sibly, et al. 2012—provide in-depth coverage of a broad range of areas. For a briefer introduction one can consult reviews, including West and Brown 2005; Enquist, et al. 2007; Price, et al. 2010; or Price, et al. 2012.

• Brown, J. H., and G. B. West, eds. 2000. Scaling in biology. Oxford: Oxford University Press.

  This edited volume helped to rekindle interest in metabolic allometry by bringing together many experts in the field to summarize current research.

• Enquist, B. J., B. H. Tiffney, and K. J. Niklas. 2007. Metabolic scaling and the evolutionary dynamics of plant size, form, and diversity: Toward a synthesis of ecology, evolution, and paleontology. International Journal of Plant Sciences 168:729–749.

  DOI: 10.1086/513479

  A nice review of allometry and metabolic scaling theory as applied to plants.

• Price, C. A., J. F. Gillooly, A. P. Allen, J. S. Weitz, and K. J. Niklas. 2010. The metabolic theory of ecology: Prospects and challenges for plant biology. New Phytologist 188.3: 696–710.

  DOI: 10.1111/j.1469-8137.2010.03442.x

  Examines MTE as applied to plants. Highlights numerous areas in which the theory has provided valuable insights into plant scaling and also identifies areas in need of further inquiry.

• Price, C. A., J. S. Weitz, V. M. Savage, et al. 2012. Testing the metabolic theory of ecology. Ecology Letters 15.12: 1465–1474.

  DOI: 10.1111/j.1461-0248.2012.01860.x

  Highlights that much more effort has gone into testing MTE predictions than has gone into evaluating its mathematical derivation and underlying assumptions. Evalutes model derivations and key assumptions for most of the prominent and active areas of MTE, highlighting both those that are robust and those that may need revision in light of empirical data.

• Sibly, R. M., J. H. Brown, and A. Kodric-Brown. 2012. Metabolic ecology: A scaling approach. Chichester, UK: Wiley-Blackwell.

  DOI: 10.1002/9781119968535

  A recent edited volume with broad coverage in topics and taxa. An excellent introduction to the current state of affairs in many areas of metabolic ecology.

• West, G. B., J. H. Brown, and B. J. Enquist. 2000. The origin of universal scaling laws in biology. In Scaling in biology. Edited by J. H. Brown and G. B. West, 87–112. Oxford: Oxford University Press.

  Explains in detail the WBE model with special attention to volume-filling, area-preserving branching and energy minimization under pulsatile and non-pulsatile flow regimes.

• West, G. B., and J. H. Brown. 2005. The origin of allometric scaling laws in biology from genomes to ecosystems: Towards a quantitative unifying theory of biological structure and organization. Journal of Experimental Biology 208.9: 1575–1592.

  DOI: 10.1242/jeb.01589

  A detailed look at the mechanistic and empirical underpinnings of MTE by two of its principal architects. Addresses many of the questions and controversies that had arisen up to that time.