1. University of Cologne, Biocenter, Institute of Zoology, General Ecology, Zuelpicher Str. 47b, D-50674 Köln, Germany.
2. Norwegian Institute for Nature Research, Høgskoleringen 9, 7034 Trondheim, Norway.
3. Norwegian University of Science and Technology, Centre for Biodiversity Dynamics, Department of Biology, Realfagbygget, NO-7491 Trondheim, Norway.