title: Mass, phylogeny, and temperature are sufficient to explain differences in metabolic scaling across mammalian orders?
abstract: Whether basal metabolic rate-body mass scaling relationships have a single exponent is highly discussed, and also the correct statistical model to establish relationships. Here, we aimed (1) to identify statistically best scaling models for 17 mammalian orders, Marsupialia, Eutheria and all mammals, and (2) thereby to prove whether correcting for differences in species' body temperature and their shared evolutionary history improves models and their biological interpretability. We used the large dataset from Sieg et al. (The American Naturalist174, 2009, 720) providing species' body mass (BM), basal metabolic rate (BMR) and body temperature (T). We applied different statistical approaches to identify the best scaling model for each taxon: ordinary least squares regression analysis (OLS) and phylogenetically informed analysis (PGLS), both without and with controlling forT. Under each approach, we tested linear equations (log-log-transformed data) estimating scaling exponents and normalization constants, and such with a variable normalization constant and a fixed exponent of either ⅔ or ¾, and also a curvature. Only under temperature correction, an additional variable coefficient modeled the influence ofTon BMR. Except for Pholidata and Carnivora, in all taxa studied linear models were clearly supported over a curvature by AICc. They indicated no single exponent at the level of orders or at higher taxonomic levels. The majority of all best models corrected for phylogeny, whereas only half of them includedT. When correcting forT, the mathematically expected correlation between the exponent (b) and the normalization constant (a) in the standard scaling modely=a xbwas removed, but the normalization constant and temperature coefficient still correlated strongly. In six taxa,Tand BM correlated positively or negatively. All this hampers a disentangling of the effect of BM,Tand other factors on BMR, and an interpretation of linear BMR-BM scaling relationships in the mammalian taxa studied.
authors.affiliation: Department of Evolutionary Ecology Institute of Zoology Johannes Gutenberg University Mainz Germany.
authors.forename: Eva Maria
authors.identifier: 0000-0003-2166-487X
authors.initials: EM
authors.lastname: Griebeler
authors.affiliation: Department of Evolutionary Ecology Institute of Zoology Johannes Gutenberg University Mainz Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Werner
keywords: Allometry; body mass; body temperature; constraints; macrophysiology; phylogeny