1. Department of Biosciences, Centre for Ecological and Evolutionary Synthesis, University of Oslo, P.O. Box 1066, N-0316 Oslo, Norway.
2. Department of Biology, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
3. Department of Animal and Aquacultural Sciences, Faculty for Biosciences, Centre for Integrative Genetics, Norwegian University of Life Sciences, P.O. Box 5003, Ås, Norway.