Environmental Correlates of Physiological Variables in Marsupials

We analyzed body temperature (Tb), basal metabolic rate (BMR), wet thermal conductance (Cwet), and evaporative water loss (EWL) of marsupials by conventional and phylogenetically corrected regression. Allometric effects were substantial for BMR, Cwet, and EWL but not Tb. There was a strong phylogenetic signal for mass and all physiological traits. A significant phylogenetic signal remained for BMR, Cwet, and EWL even after accounting for the highly significant phylogenetic signal of mass. Tb, BMR, Cwet, and EWL allometric residuals were correlated with some diet, distribution, and climatic variables before and after correction for phylogeny. Tb residuals were higher for marsupials from arid environments (high Ta and more variable rainfall). The fossorial marsupial mole had a lower-than-expected Tb residual. The allometric slope for BMR was 0.72-0.75. Residuals were consistently related to distribution aridity and rainfall variability, with species from arid and variable rainfall habitats having a low BMR, presumably to conserve energy in a low-productivity environment. The nectarivorous honey possum had a higher-than-expected BMR. For Cwet, the allometric slope was 0.55-0.62; residuals were related to diet, with folivores having low and insectivores high Cwet residuals. The allometric slope for EWL was 0.68-0.73. EWL residuals were consistently correlated with rainfall variability, presumably facilitating maintenance of water balance during dry periods.