1. Department of Ecology, Section of Plant Ecology and Systematics, Lund University, Ecology Building, SE‐22362 Lund, Sweden
2. Department of Ecology and Environmental Science, Umeå University, SE‐901 87 Umeå, Sweden
3. Department of Biology, University of Oulu, P.O. Box 3000, FI‐90014 Oulu, Finland
4. Biological Institute, University of Bergen, Allegaten 41, NO‐5007 Bergen, Norway
5. Section of Ecology, Department of Biology, University of Turku, FI‐200 14 Turku, Finland
6. Department of Zoology, Stockholm University, SE‐106 91 Stockholm, Sweden