1. Department of Geography, University of Oregon, Eugene, Oregon 97403, USA
2. Ecosystem Science and Management Program, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia V2N 4Z9, Canada
3. Royal British Columbia Museum, 675 Belleville Street, Victoria, British Columbia V8W 9W2, Canada, and Department of Biology and School of Earth and Ocean Sciences, University of Victoria, P.O. Box 1700, Victoria, British Columbia V8W 2Y2, Canada