Abstract
The scaling of metabolic rates to body size is widely considered to be of great biological and ecological importance, and much attention has been devoted to determining its theoretical and empirical value. Most debate centers on whether the underlying power law describing metabolic rates is 2/3 (as predicted by scaling of surface area/volume relationships) or 3/4 ("Kleiber's law"). Although recent evidence suggests that empirically derived exponents vary among clades with radically different metabolic strategies, such as ectotherms and endotherms, models, such as the metabolic theory of ecology, depend on the assumption that there is at least a predominant, if not universal, metabolic scaling exponent. Most analyses claimed to support the predictions of general models, however, failed to control for phylogeny. We used phylogenetic generalized leastsquares models to estimate allometric slopes for both basal metabolic rate (BMR) and field metabolic rate (FMR) in mammals. Metabolic rate scaling conformed to no single theoretical prediction, but varied significantly among phylogenetic lineages. In some lineages we found a 3/4 exponent, in others a 2/3 exponent, and in yet others exponents differed significantly from both theoretical values. Analysis of the phylogenetic signal in the data indicated that the assumptions of neither specieslevel analysis nor independent contrasts were met. Analyses that assumed no phylogenetic signal in the data (specieslevel analysis) or a strong phylogenetic signal (independent contrasts), therefore, returned estimates of allometric slopes that were erroneous in 30% and 50% of cases, respectively. Hence, quantitative estimation of the phylogenetic signal is essential for determining scaling exponents. The lack of evidence for a predominant scaling exponent in these analyses suggests that general models of metabolic scaling, and macroecological theories that depend on them, have little explanatory power.
Original language  English 

Pages (fromto)  27832793 
Number of pages  11 
Journal  Ecology 
Volume  91 
Issue number  9 
DOIs  
Publication status  Published  01 Sep 2010 
Keywords
 Allometry
 Basal metabolic rate. (BMR)
 Field metabolic rate (FMR)
 Kleiber's law
 Metabolic theory of ecology (MTE)
 Phylogenetic comparative analysis
 Phylogenetic generalized least squares
 Phylogeneticatty independent contrasts
 Phylogeny
 Power law
 Scaling
ASJC Scopus subject areas
 Ecology, Evolution, Behavior and Systematics
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Prizes

BBSRC/NERC Research Grant (£312K; BB/E014593/1; 50% ownership)
Capellini, Isabella (Recipient), 01 Jan 2008
Prize: Prize (including medals and awards)