1. School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 IUG, UK
2. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
3. Experimental Ecology, ETH Zurich, ETH Zentrum NW, CH–8092 Zurich, Switzerland
4. Centre for Mathematical Biology, Department of Mathematical Sciences, University of Bath, Bath BA2 7AY, UK
5. Centre for Mathematical Biology, Mathematical Institute, University of Oxford, 24–29 St Giles, Oxford OX1 3LB, UK