1. Department of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA;
2. Current affiliation: Department of Ecology and Evolution, University of Connecticut, Storrs, Connecticut 06268, USA;
3. Redpath Museum, McGill University, Montreal, Quebec H3A 2K6, Canada;
4. Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California 95060, USA;
5. Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland;