Effects of Contingency versus Constraints on the Body-Mass Scaling of Metabolic Rate

Douglas S. Glazier
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Douglas S. Glazier: Department of Biology, Juniata College, Huntingdon, PA 16652, USA

Challenges, 2018, vol. 9, issue 1, 1-14

Abstract: I illustrate the effects of both contingency and constraints on the body-mass scaling of metabolic rate by analyzing the significantly different influences of ambient temperature (T a ) on metabolic scaling in ectothermic versus endothermic animals. Interspecific comparisons show that increasing T a results in decreasing metabolic scaling slopes in ectotherms, but increasing slopes in endotherms, a pattern uniquely predicted by the metabolic-level boundaries hypothesis, as amended to include effects of the scaling of thermal conductance in endotherms outside their thermoneutral zone. No other published theoretical model explicitly predicts this striking variation in metabolic scaling, which I explain in terms of contingent effects of T a and thermoregulatory strategy in the context of physical and geometric constraints related to the scaling of surface area, volume, and heat flow across surfaces. My analysis shows that theoretical models focused on an ideal 3/4-power law, as explained by a single universally applicable mechanism, are clearly inadequate for explaining the diversity and environmental sensitivity of metabolic scaling. An important challenge is to develop a theory of metabolic scaling that recognizes the contingent effects of multiple mechanisms that are modulated by several extrinsic and intrinsic factors within specified constraints.

Keywords: allometry; body size; contextual multimodal theory; ectothermic vs. endothermic animals; metabolism; metabolic-level boundaries hypothesis; scaling; thermal conductance; thermoregulation (search for similar items in EconPapers)
JEL-codes: A00 C00 Z00 (search for similar items in EconPapers)
Date: 2018
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