1. Department of Biology; Duke University; Durham North Carolina 27708
2. Current Address: Chicago Botanic Garden; 1000 Lake Cook Road Glencoe Illinois 60022
3. Department of Plant Ecology and Evolution; Evolutionary Biology Centre; Uppsala University; Norbyvägen 18D SE-752 36 Uppsala Sweden
4. School of Geography and Earth Sciences; McMaster University; Hamilton Ontario Canada
5. Department of Aquatic Sciences and Assessment; Swedish University of Agricultural Sciences; SE-750 07 Uppsala Sweden
6. Department of Biology; University of Eastern Finland; P.O. Box 111 80101 Joensuu Finland
7. Department of Plant Sciences and Northern Research Center (CEN); Laval University Quebec; Canada
8. Department of Natural History, Norwegian University of Science and Technology University Museum; Trondheim Norway