1. School of Plant Science, University of Tasmania, Private Bag 55, Hobart 7001, Tas., Australia
2. Department of Ecology and Evolutionary Biology, 569 Dabney Hall, University of Tennessee, Knoxville, TN 37996, USA
3. (Author for correspondence:)
4. CRC for Forestry, Private Bag 12, Hobart 7001, Tas., Australia
5. Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK
6. Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
7. Merriam‐Powell Center for Environmental Research, Flagstaff, AZ 86011, USA