Parts of Australia are teeming with over-abundant herbivores, such as feral goats and native kangaroos. But is shooting the best approach? Or can a well-managed dingo population lead to a well-managed kangaroo population?
Authors: Donna B Harris, Stephen D Gregory, Barry W Brook, Euan G Ritchie, David B Croft, Graeme Coulson and Damien A Fordham.
Species distribution models have come under criticism for being too simplistic for making robust future forecasts, partly because they assume that climate is the main determinant of geographical range at large spatial extents and coarse resolutions, with non-climate predictors being important only at finer scales.
We suggest that this paradigm might be obscured by species movement patterns.
To explore this we used contrasting kangaroo (family Macropodidae) case studies: two species with relatively small, stable home ranges (Macropus giganteus and M. robustus) and three species with more extensive, adaptive ranging behaviour (M. antilopinus, M. fuliginosus and M. rufus).We predicted that non-climate predictors will be most influential to model fit and predictive performance at local spatial resolution for the former species and at landscape resolution for the latter species.
We compared residuals autocovariate – boosted regression tree (RAC-BRT) model statistics with and without species-specific non-climate predictors (habitat, soil, fire, water and topography), at local- and landscape-level spatial resolutions (5 and 50 km).
As predicted, the influence of non-climate predictors on model fit and predictive performance (compared with climate-only models) was greater at 50 compared with 5 km resolution for M. rufus and M. fuliginosus and the opposite trend was observed for M. giganteus.T he results for M. robustus and M. antilopinus were inconclusive. Also notable was the difference in inter-scale importance of climate predictors in the presence of non-climate predictors.
In conclusion, differences in autecology, particularly relating to space use, may contribute to the importance of non-climate predictors at a given scale, not model scale per se. Further exploration of this concept across a range of species is encouraged and findings may contribute to more effective conservation and management of species at ecologically meaningful scales.
Harris DB, Gregory SD, Brook BW, Ritchie EG, Croft DB, Coulson G, Fordham DA (2014) The influence of non-climate predictors at local and landscape resolutions depends on the autecology of the species. Austral Ecology PDF DOI
Authors: Mark D B Eldridge, Sally Potter, Christopher N Johnson and Euan G Ritchie
Tropical savannas cover 20–30% of the world’s land surface and exhibit high levels of regional endemism, but the evolutionary histories of their biota remain poorly studied.
The most extensive and unmodified tropical savannas occur in Northern Australia, and recent studies suggest this region supports high levels of previously undetected genetic diversity.To examine the importance of barriers to gene flow and the environmental history of Northern Australia in influencing patterns of diversity, we investigated the phylogeography of two closely related, large, vagile macropodid marsupials, the antilopine wallaroo (Macropus antilopinus; n=78), and the common wallaroo (Macropus robustus; n=21). Both species are widespread across the tropical savannas of Australia except across the Carpentarian Barrier (CB) where there is a break in the distribution of M. antilopinus.
We determined sequence variation in the hypervariable Domain I of the mitochondrial DNA control region and genotyped individuals at 12 polymorphic microsatellite loci to assess the historical and contemporary influence of the CB on these species. Surprisingly, we detected only limited differentiation between the disjunct Northern Territory and Queensland M. antilopinus populations. In contrast, the continuously distributed M. robustus was highly divergent across the CB.
Although unexpected, these contrasting responses appear related to minor differences in species biology. Our results suggest that vicariance may not explain well the phylogeographic patterns in Australia’s dynamic monsoonal environments. This is because Quaternary envi- ronmental changes in this region have been complex, and diverse individual species’ biologies have resulted in less predictable and idiosyncratic responses.
Eldridge MDB, Potter S, Johnson CN, Ritchie EG (2014) Differing impact of a major biogeographic barrier on genetic structure in two large kangaroos from the monsoon tropics of Northern Australia, Ecology and Evolution PDF DOI