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Resting vs. active: a meta‐analysis of the intra‐ and inter‐specific associations between minimum, sustained, and maximum metabolic rates in vertebrates
Author(s) -
Auer Sonya K.,
Killen Shaun S.,
Rezende Enrico L.
Publication year - 2017
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1111/1365-2435.12879
Subject(s) - biology , metabolic rate , vertebrate , generality , meta analysis , ecology , energy expenditure , medicine , genetics , endocrinology , gene , psychology , psychotherapist
Summary Variation in aerobic capacity has far reaching consequences for the physiology, ecology, and evolution of vertebrates. Whether at rest or active, animals are constrained to operate within the energetic bounds determined by their minimum (min MR ) and sustained or maximum metabolic rates (upper MR ). Min MR and upper MR can differ considerably among individuals and species but are often presumed to be mechanistically linked to one another. Specifically, min MR is thought to reflect the idling cost of the machinery needed to support upper MR . However, previous analyses based on limited datasets have come to conflicting conclusions regarding the generality and strength of their association. Here we conduct the first comprehensive assessment of their relationship, based on a large number of published estimates of both the intra‐specific ( n = 176) and inter‐specific ( n = 41) phenotypic correlations between min MR and upper MR , estimated as either exercise‐induced maximum metabolic rate ( VO 2 max), cold‐induced summit metabolic rate (Msum), or daily energy expenditure ( DEE ). Our meta‐analysis shows that there is a general positive association between min MR and upper MR that is shared among vertebrate taxonomic classes. However, there was stronger evidence for intra‐specific correlations between min MR and Msum and between min MR and DEE than there was for a correlation between min MR and VO 2 max across different taxa. As expected, inter‐specific correlation estimates were consistently higher than intra‐specific estimates across all traits and vertebrate classes. An interesting exception to this general trend was observed in mammals, which contrast with birds and exhibit no correlation between min MR and Msum. We speculate that this is due to the evolution and recruitment of brown fat as a thermogenic tissue, which illustrates how some species and lineages might circumvent this seemingly general association. We conclude that, in spite of some variability across taxa and traits, the contention that min MR and upper MR are positively correlated generally holds true both within and across vertebrate species. Ecological and comparative studies should therefore take into consideration the possibility that variation in any one of these traits might partly reflect correlated responses to selection on other metabolic parameters. A lay summary is available for this article.