1. 2Department of Botany, Norwegian University of Science and Technology, N‐7034 Trondheim, Norway, and Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99775‐7000; and
2. 3Department of Biology, University of Massachusetts, Amherst, Massachusetts 01003‐5810; and
3. 4Institute for Environmental Studies, University of Wisconsin, Madison, Wisconsin 53706; and
4. 5Department of Biology, University of Missouri, 8001 Natural Bridge Rd, St. Louis, Missouri 63121; and
5. 6School of Environment, Duke University, Durham, North Carolina 27708