1. Norwegian Institute for Nature Research (NINA), Department of Arctic Ecology, Storgata 25, N‐9005 Tromsø, Norway, and Biology Department, Faculty of Mathematical and Natural Sciences, University of Tromsø, N‐9037 Tromsø, Norway;
2. Department of Zoology, Norwegian University of Science and Technology, N‐7034 Trondheim, Norway, and Norwegian Institute for Nature Research, Tungasletta 2, N‐7005 Trondheim, Norway; and
3. Norwegian Institute for Nature Research, Tungasletta 2, N‐7005 Trondheim, Norway