ASSESSING HOW POSSUMS RECORD THEIR LOCAL DIET AND ENVIRONMENT VIA STABLE ISOTOPES AND DENTAL MICROWEAR TEXTURES WITH IMPLICATIONS FOR PALEOECOLOGICAL ANALYSES

Australia’s geological and paleontological record shows long-term aridification, making it a particularly interesting system to assess long-term responses to climate change. Geochemical analysis of tooth enamel as well as dental microwear texture analysis (DMTA) can provide a proxy for the vegetation an organism encountered and consumed and the climate it occupied across its range. The particular climatic or environmental signal captured in a taxon’s dentition may differ based on its drinking behavior, physiology, and food source (e.g. the isotopic difference between C₃ and C₄ plants or the physical difference between grasses and woody browse). Therefore, it is first necessary to examine the relationship between climatic and dietary variables and the isotopic and DMTA signal recorded on or in teeth in related modern organisms.

Small arboreal marsupials were abundant during the Miocene when Australian forests were more widely distributed and declined with the opening up of the landscape. Most paleoecological analyses in Australia have focused on ground dwelling marsupials, in part because an extant baseline is not well developed. Here, we analyzed stable carbon and oxygen isotope data from incisor enamel and DMTA of the cheek teeth of two small, arboreal, primarily folivorous marsupials, Trichosurus vulpecula and Trichosurus caninus. We find that T. vulpecula stable oxygen isotope values are best predicted by a combination of relative humidity, maximum mean annual temperature, and δ¹⁸O_{precipitation} (R² = 0.24, p < 0.001), while stable carbon values have a best fit model that includes relative humidity, maximum mean annual temperature, and mean annual precipitation (R² = 0.18, p < 0.001). In contrast, mean annual precipitation is the best predictor of stable oxygen isotopes in T. caninus (R² = 0.42, p = 0.006), while no variables tested predicted stable carbon values in this highly restricted species. Analysis of the microwear of T. vulpecula indicate the consumption of tough food items with some individuals eating harder food items, consistent with observational data. Understanding how possums track their environment today opens up possibilities for better climate and environment reconstructions in Australia’s fossil record.