1. Department of Animal and Plant Sciences; University of Sheffield; Western Bank; Sheffield; S10 2TN; UK
2. Centre for Ecology and Hydrology Bangor; Environment Centre Wales; Deiniol Road; Bangor; North Wales; LL57 2UW; UK
3. The James Hutton Institute; Craigiebuckler; Aberdeen; AB15 8QH; UK
4. School of Science and the Environment; Manchester Metropolitan University; Manchester; M15GD; UK
5. Centre for Ecology and Hydrology Edinburgh; Bush Estate; Penicuik; EH26 0QB; UK
6. Environment Department; University of York; York; YO10 5DD; UK
7. Division of Biology; Imperial College London; Silwood Park; Ascot; Berkshire; SL5 7PY; UK