1. Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
2. Alaska Cooperative Fish and Wildlife Unit, US Geological Survey, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
3. USDA Forest Service, Pacific Northwest Research Station, Boreal Ecology Cooperative Research Unit, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
4. Department of Botany, University of Florida, P.O. Box 118526, Gainesville, FL 32611-8526, USA.
5. Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK S7N 5E2, Canada.