On the Interplay among Ambient Temperature, Basal Metabolic Rate, and Body Mass

Area of Science:

• Metabolic studies
• Physiological ecology
• Mammalian metabolism

Background:

• Ecological studies indicate a negative correlation between ambient temperature and mass-independent basal metabolic rate (BMR) in endotherms.
• Ambient temperature is widely considered a primary driver of residual BMR evolution.
• The size dependence of this relationship and potential sampling biases are not well understood.

Purpose of the Study:

• To investigate the size dependence of the relationship between ambient temperature and mass-independent BMR in mammals.
• To determine if body mass influences the effect of ambient temperature on residual BMR.

Main Methods:

• Utilized published data for 458 mammal species, including body mass (mb), BMR, and annual mean temperature (Tmean).
• Employed statistical analysis to examine the interaction between mb and Tmean as predictors of residual BMR.

Main Results:

• A significant interaction between body mass and mean annual temperature was found to affect residual BMR.
• The influence of mean annual temperature on residual BMR diminishes as body mass increases.
• The explanatory power of Tmean for residual BMR variance decreased with increasing body mass, from 20%-30% for species under 100g to nearly 0% for species over 1,000g.

Conclusions:

• The impact of ambient temperature on the evolution of residual BMR in endotherms may be overestimated due to the prevalence of small-bodied species in datasets.
• Future research should account for body mass when assessing the role of ambient temperature in metabolic evolution.
• Sampling biases in physiological data sets, particularly the overrepresentation of small species, may skew our understanding of metabolic adaptation drivers.