Environmental Correlates of Physiological Variables in Marsupials

We analyzed body temperature (T-b), basal metabolic rate (BMR), wet thermal conductance (C-wet), and evaporative water loss (EWL) of marsupials by conventional and phylogenetically corrected regression. Allometric effects were substantial for BMR, C-wet, and EWL but not T-b. There was a strong phylogenetic signal for mass and all physiological traits. A significant phylogenetic signal remained for BMR, C-wet, and EWL even after accounting for the highly significant phylogenetic signal of mass. T-b, BMR, C-wet, and EWL allometric residuals were correlated with some diet, distribution, and climatic variables before and after correction for phylogeny. T-b residuals were higher for marsupials from arid environments (high T-a and more variable rainfall). The fossorial marsupial mole had a lower-than-expected T-b 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 C-wet, the allometric slope was 0.55-0.62; residuals were related to diet, with folivores having low and insectivores high C-wet 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.