Climatic Adaptation and the Evolution of Basal and Maximum Rates of Metabolism in Rodents

Abstract

Abstract. Metabolic rate is a key aspect of organismal biology and the identification of selective factors that have led to species differences is a major goal of evolutionary physiology. We tested whether environmental characteristics and/or diet were significant predictors of interspecific variation in rodent metabolic rates. Mass-specific basal metabolic rates (BMR) and maximum metabolic rates (MMR, measured during cold exposure in a He-O 2 atmosphere) were compiled from the literature. Maximum (Tmax) and minimum (Tmin) annual mean temperatures, latitude, altitude, and precipitation were obtained from field stations close to the capture sites reported for each population (N ϭ 57). Diet and all continuous-valued traits showed statistically significant phylogenetic signal, with the exception of masscorrected MMR and altitude. Therefore, results of phylogenetic analyses are emphasized. Body mass was not correlated with absolute latitude, but was positively correlated with precipitation in analyses with phylogenetically independent contrasts. Conventional multiple regressions that included body mass indicated that Tmax (best), Tmin, latitude, and diet were significant additional predictors of BMR. However, phylogenetic analyses indicated that latitude was the only significant predictor of mass-adjusted BMR (positive partial regression coefficient, one-tailed P ϭ 0.0465). Conventional analyses indicated that Tmax, Tmin (best), and altitude explained significant amounts of the variation in mass-adjusted MMR. With body mass and Tmin in the model, no additional variables were significant predictors. Phylogenetic contrasts yielded similar results. Both conventional and phylogenetic analyses indicated a highly significant positive correlation between residual BMR and MMR (as has also been reported for birds), which is consistent with a key assumption of the aerobic capacity model for the evolution of vertebrate energetics (assuming that MMR and exercise-induced maximal oxygen consumption are positively functionally related). Our results support the hypothesis that variation in environmental factors leads to variation in the selective regime for metabolic rates of rodents. However, the causes of a positive association between BMR and latitude remain obscure. Moreover, an important area for future research will be experiments in all taxa are raised under common conditions to allow definitive tests of climatic adaptation in endotherm metabolic rates and to elucidate the extent of adaptive phenotypic plasticity.Key words. Bergmann's rule, body size, comparative method, diet, endothermy, energetics, temperature.Received August 29, 2003. Accepted February 8, 2004 Identification of the selective factors that have led to interspecific diversification in metabolic rates has been a major goal of ecological and evolutionary physiology (Garland and Carter 1994;Spicer and Gaston 1999;Walters and Reich 2000;McNab 2002). The most common approach is to correlate species or population differences in metabolic rate with variation in var...

Kidney Mass and Relative Medullary Thickness of Rodents in Relation to Habitat, Body Size, and Phylogeny

“…Nevertheless, results of conventional and phylogenetic analyses were largely congruent, with one interesting exception (see below). Although body mass showed significant phylogenetic signal, as has been reported previously for rodents and other animal groups Blomberg et al 2003;Rezende et al 2004), rodents categorized as aquatic (nutria, beaver, muskrat, water rat) were significantly larger in body mass as compared with species from all other habitat types. Thus, both ecology and phylogeny affect body size.…”

“…As will be shown, our analyses were in fact able to demonstrate associations with habitat. Clearly, an improvement for future studies would be to obtain quantitative environmental measurements from at or near the capture sites of each species (Tieleman et al 2003;Rezende et al 2004).…”

A strong response to selection on mass-independent maximal metabolic rate without a correlated response in basal metabolic rate

“…A number of studies have suggested that BMR would likely show a correlated response to direct selection on MMR (Koteja, 1987;Bozinovic, 1992;Dohm et al, 2001;Rezende et al, 2004;Nesoplo et al, 2005a;Sadowska et al, 2005;Wone et al, 2009). Likewise many evolutionary models suggest complex interrelationships among traits linked to metabolic rates (Ricklefs and Wikelski, 2002;Downs et al, 2013).…”

“…For example, is there a universal metabolic scaling law, why is resting metabolism correlated with daily energy use in mammals but not birds, how did the diverse resting and maximal metabolic rates of animals evolve and is there a necessary correlation between resting and maximal aerobic metabolism in vertebrates (Ricklefs et al, 1996;Clavijo-Baque and Bozinovic, 2012)? Some of these questions are very difficult to answer but ecological and evolutionary physiologists have recently made increasing use of artificial selection experiments to test hypotheses about the phenotypic and genetic integration of energy metabolism (Swallow et al, 1998;Koch and Britton, 2001;Ksiażek et al, 2004;Rezende et al, 2004;Sadowska et al, 2005Sadowska et al, , 2008Swallow et al, 2009;Wone et al, 2009;Gebczyński and Konarzewski 2009a, b,). One of the foci of these recent studies has been testing hypotheses about the evolution of endothermy.…”

Associations between basal metabolic rate and reproductive performance in C57BL/6J mice

“…Despite the expectation that it would reflect some minimal level of homeostatic cellular processes, BMR shows tremendous variability both between and within species (McNab, 2005;Rezende et al, 2004;Snodgrass et al, 2005), raising two key issues: why does the variation exist and what are the functional implications of the variability? Clearly, an individual with a high BMR would need to feed for longer to fuel its metabolism than one with a low BMR.…”