Conservation status and biogeography of Australia's terrestrial mammals

Abstract

This paper attempts to identify and explain patterns in the biogeography of Australia’s indigenous terrestrial mammals at the time of European settlement (before modern extinctions), and also compares species’ pre-European and current status by region. From subfossil, historical and contemporary sources, we compiled data on the past geographic range and present status of mammals for Australia’s 85 biogeographic regions. Of the 305 indigenous species originally present, 91 have disappeared from at least half of the bioregions in which they occurred before European settlement. Thirty-nine extant species ‘persist’ in less than 25% of their original bioregions; 28 of these are marsupials and 11 are rodents. Twenty-two of the original 305 species are extinct, a further eight became restricted to continental islands, and 100 have become extinct in at least one bioregion. Over the same period, 26 species of exotic mammals established wild populations and now occupy from one to 85 bioregions. When we classified the bioregions in terms of their original species composition, the 3-group level in the dendrogram approximated the Torresian, Eyrean and Bassian subregions proposed by Spencer in 1898, while the 4-group level separated southern semiarid Eyrean bioregions, including those in south-west Australia, from the arid Eyrean bioregions. The classification dendrogram showed geographically (and statistically) discrete clustering down to the 19-group level, suggesting that all four subregions can be further divided on the basis of their mammal faunas. Variation partitioning showed 66% of the biogeographical pattern can be explained by environmental factors (related to temperature and precipitation), the spatial position of each bioregion (a third-order polynomial of latitude and longitude), the area of each bioregion, and the richness of species in each bioregion. In addition to the marked distributional changes that indigenous mammals have experienced over the last 200 years, the 49% of variation explainable by temperature and precipitation implies further shifts with global climate change.

There is a critical weight range for Australia's declining tropical mammals

“…Biogeogr. ) Burbidge et al (2008), applied here to native non-flying mammals. A separate value is calculated for each of Australia's 85 biogeographic regions.…”

“…Their primary conclusion was that there is no mid-sized critical weight range (CWR) for tropical marsupials, in stark contrast to the pattern observed in central and southern Australia, where marsupial declines are strongly concentrated in the CWR. However, we demonstrate here, using both the original dataset of Fisher et al (provided as online supporting information by those authors) and an independent dataset (Burbidge et al, 2008), that there is a very clear CWR for northern Australian mammals, consistent with the wellaccepted range of 35−5500 g for Australian mammals across the continent more broadly.…”

“…We also examined an independent dataset, that of Burbidge et al (2008), to further validate the result we obtained using the dataset of Fisher et al For each of Australia's 85 biogeographic regions (Fig. 2), Burbidge et al (2008) classified the current status of each mammal species present at the time of European colonization as: (1) persistent (< 50% range decline); (2) in decline (50-90% range decline); (3) in severe decline (> 90% range decline); or (4) extinct.…”

“…2), Burbidge et al (2008) classified the current status of each mammal species present at the time of European colonization as: (1) persistent (< 50% range decline); (2) in decline (50-90% range decline); (3) in severe decline (> 90% range decline); or (4) extinct. The status classification is specific to each bioregion, rather than bs_bs_banner Global Ecology and Biogeography, (Global Ecol.…”

“…The FAI is calculated as: (N + E -P)/2N, where N is the number of species originally present, E is the number of extinct species and P is the number of species persisting in > 50% of their original range. To calculate FAI, N, E and P for each bioregion were obtained from Appendix 1 of Burbidge et al (2008). (b) The distribution of the non-native red fox.…”