title: Energy in-equivalence in Australian marsupials: evidence for disruption of the continent's mammal assemblage, or are rules meant to be broken?
abstract: The energy equivalence rule (EER) is a macroecological hypothesis that posits that total population energy use (PEU) should be independent of species body mass, because population densities and energy metabolisms scale with body mass in a directly inverse manner. However, evidence supporting the EER is equivocal, and the use of basal metabolic rate (BMR) in such studies has been questioned; ecologically-relevant indices like field metabolic rate (FMR) are probably more appropriate. In this regard, Australian marsupials present a novel test for the EER because, unlike eutherians, marsupial BMRs and FMRs scale differently with body mass. Based on either FMR or BMR, Australian marsupial PEU did not obey an EER, and scaled positively with body mass based on ordinary least squares (OLS) regressions. Importantly, the scaling of marsupial population density with body mass had a slope of -0.37, significantly shallower than the expected slope of -0.75, and not directly inverse of body-mass scaling exponents for BMR (0.72) or FMR (0.62). The findings suggest that the EER may not be a causal, universal rule, or that for reasons not yet clear, it is not operating for Australia's unique native fauna.
authors: Institute of Conservation Biology and Environmental Management, School of Biological Science, University of Wollongong, Wollongong, Australia. amunn@uow.edu.au
authors: Adam J
authors: AJ
authors: Munn
authors: Craig
authors: C
authors: Dunne
authors: Dennis W H
authors: DW
authors: Müller
authors: Marcus
authors: M
authors: Clauss
mesh_terms: D000818:Animals; D001315:Australia; D001481:Basal Metabolism / Q000502:physiology; D001835:Body Weight; D004734:Energy Metabolism / Q000502:physiology*; D008394:Marsupialia / Q000502:physiology*; D011156:Population Density; D012044:Regression Analysis