A multiproxy approach to tracking aridity across Australian landscapes using brushtail possums (Marsupialia: Phalangeridae: Trichosurus)

Abstract

Australia’s geological and paleontological record shows long-term aridification, making it a particularly interesting system in which to assess long-term responses to climate change. Geochemical analyses of tooth enamel, as well as dental microwear texture analysis (DMTA), can provide a proxy for the vegetation an organism consumed and the climate it occupied during its life. The way in which a taxon’s dentition tracks its environment can differ based on physiology, diet, and drinking behavior; thus, relationships between environmental variables and proxy data must first be tested in modern organisms. While most analyses focus on large ground-dwelling mammals, here, enamel stable carbon and oxygen isotopes and molar DMTA variables (anisotropy and complexity) of two medium-sized arboreal marsupials (Trichosurus vulpecula and Trichosurus caninus) were examined. While stable oxygen isotopes are best modeled by temperature, relative humidity, and precipitation, stable carbon isotopes are best modeled by temperature, relative humidity, and enhanced vegetation index. Anisotropy shows a weak positive relationship with temperature, but complexity was unrelated to any climate or environmental attributes, including aridity. Trichosurus stable oxygen isotopes track relative aridity across Australia, albeit with a slightly weaker relationship than other examined arboreal and ground-dwelling marsupials (e.g. koalas and kangaroos). Dental microwear textures appear to reflect the diet of the possum, not environmental grit consumed with food items. Collectively, brushtail possums and their ancestors may still provide valuable information in paleoecological reconstructions of ancient Australian environments.