1. Laboratoire d'Ecologie, UMR 7625, Ecole Normale Supérieure, 46 rue d'Ulm, F–75230 Paris Cedex 05, France.
2. Department of Zoology, University of Washington, 24 Kincaid Hall, Box 351800, Seattle, WA 98195–1800, USA.
3. Department of Ecology and Crop Production Science, Swedish University of Agricultural Sciences, Box 7043, SE–750 07 Uppsala, Sweden.
4. Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK.
5. NERC Centre for Population Biology, Imperial College at Silwood Park, Ascot, Berks, SL5 7PY, UK.
6. Department of Biology, Western Washington University, 516 High Street, Bellingham, WA 98225–9160, USA.
7. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831–6400, USA.
8. Environment Department, University of York, York, YO10 5DD, UK.
9. Institut für Umweltwissenschaften, Universität Zürich, Winterthurerstrasse 190, CH–8057 Zürich, Switzerland.
10. Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN 55108, USA.