1. Desert Ecology Research Group, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
2. School of Life and Environmental Sciences, Deakin University (Burwood Campus), Geelong, Victoria 3125, Australia
3. Global Trophic Cascades Program, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA
4. School of Environmental and Forest Sciences, University of Washington, Seattle, WA 98195, USA