1. Department of Zoology, University of OxfordSouth Parks Road, Oxford OX1 3PS, UK
2. Department of Biological Sciences, Lancaster Environment Centre, Lancaster UniversityLancaster LA1 4YQ, UK
3. Natural Environment Research Council Centre for Ecology and HydrologyMansfield Road, Oxford OX1 3SR, UK
4. Department of Biology, Algoma University College, Laurentian University1520 Queen Street East, Sault Sainte Marie, Ont. P6A 2G4, Canada
5. Ecology, Evolution and Behaviour Section, School of Biological SciencesPrivate Bag 92019, University of Auckland, Auckland, New Zealand
6. School of Biological Sciences, University of SydneyHeydon-Laurence Building, A08, Sydney 2006, Australia