1. Department of Biology, Concordia University, 7141 Sherbrooke St. West, Montreal, Quebec H4B1R6, Canada
2. Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway
3. Ecosystems and Ecology, Natural Resources Institute of Finland (Luke), 99910, Finland
4. Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, Helsinki, Finland