Higher extinction rates of dasyurids on Australo-Papuan continental shelf islands and the zoogeography of New Guinea mammals

Aim: Contemporary patterns of mammalian species richness on islands are influenced by well-understood biogeographical variables. Whether or not mammalian orders differ in their rates of persistence, however, remains uncertain. Our aims were to assess the persistence of four mammalian orders on Australo-Papuan continental shelf islands in relation to the faunas within adjacent zoogeographic provinces. We also aimed to define New Guinea's mammalian zoogeographic provinces quantitatively. Location: New Guinea and 274 Australo-Papuan continental shelf islands. Methods: We compiled 4194 distributional records for 264 of New Guinea's native mammals. Records were allocated to existing mapped bioregions. We used cluster analysis to allocate bioregions to zoogeographic provinces. Using generalized linear models, we determined the persistence of insular mammals as proportions of the species present within adjacent zoogeographic provinces. Persistence rates were calculated for four major orders (Dasyuromorphia, Diprotodontia, Peramelemorphia and Rodentia). Results: The classification dendrogram grouped New Guinea's bioregions into three areas corresponding to the Oceanic, Tumbanan and Austral provinces. In all but two zoogeographic provinces, the proportions of Dasyuromorphia persisting on islands were lower than other orders. Overall, species of Dasyuromorphia were much less likely to persist on Australo-Papuan continental shelf islands. Main conclusions: Unlike the other orders considered, dasyuromorphs are carnivorous and insectivorous and require large home ranges relative to body size. We suggest that the resulting low population densities might expose species in this order to higher rates of extinction on islands. Translocations of threatened mammals to predator-free islands are common, but our results suggest that insurance populations of threatened dasyurids on small islands may be less secure than translocations of other taxa. Our results support calls for insurance populations of the rapidly declining dasyurid, the Tasmanian devil (Sarcophilus harrisii), to be established on mainland Australia rather than on islands alone.