USING DIETARY ECOLOGY TO EXAMINE THE IMPACTS OF NON-NATIVE SPECIES ON AUSTRALIAN MARSUPIAL HERBIVORES

European arrival into Australia had large scale impacts on the local flora and fauna. Most notably, Europeans brought with them numerous non-native species, including the European red fox and rabbits. The introduction of these species had significant consequences on native Australian mammals, causing some small to medium sized herbivores to exist largely on islands. Here, we examined the dietary ecology of two native marsupial herbivores, Setonix brachyurus and Petrogale lateralis, which have restricted ranges in Western Australia. Pleistocene fossils from southwest Australia were compared to extant specimens, with additional comparisons between island and mainland populations in extant specimens (when possible). Dental microwear textures of P. lateralis are indistinguishable across space/time for both anisotropy (p = 0.067) and complexity (p = 0.342), and consistent with the consumption of a browse dominated diet. Similarly, S. brachyurus maintains a browsing diet through time on the mainland (from the Pleistocene to the present), but modern island populations demonstrate a significant increase in anisotropy values (p = 0.038) compared to modern mainland populations. This difference suggests that modern island S. brachyurus populations are potentially inhabiting less preferential habitats and eating drier, tougher foods. Stable isotope analysis of S. brachyurus shows significantly greater carbon and oxygen isotope values (from tooth enamel) on islands as compared to extant populations from mainland Western Australia (δ¹³C p = 0.002, δ¹⁸O p = 0.006). These data suggest that quokkas feed in slightly more open and arid environments on islands where non-native predators are absent. Collectively, dental microwear textures indicative of a browse diet and highly negative carbon isotope values (all values range from -20.6‰ to -15.5‰) suggest that these dense forest/shrub browsers maintained similar dietary ecology across space and since the Pleistocene. Similarities in the dietary ecology of these taxa across space and through time, with a slight shift towards less favorable habitats in S. brachyurus when living on islands lacking foxes, suggests that restricted ranges of these taxa today are most likely a result of the predation of non-native carnivorans and/or other human influences.