1 Community Ecology Unit, Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
2 School of Architecture, Civil and Environmental Engineering ENAC, École Polytechnique Fédérale de Lausanne EPFL, Station 2, 1015 Lausanne, Switzerland.
3 Department of Ecology, Montana State University, 1156-1174 S 11th Ave, Bozeman, MT 59717, USA.
4 CEAM Foundation, Joint Research Unit University of Alicante-CEAM, Dept Ecology, University of Alicante, Carr. de San Vicente del Raspeig, PO Box 99, 03080 Alicante, Spain.