1. School of Earth and Environmental Sciences, Michael Smith Building, The University of Manchester, Manchester M13 9PT, UK
2. Department of Terrestrial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB Wageningen, The Netherlands
3. Laboratory of Nematology, Wageningen University, PO Box 8123, 6700 ES, Wageningen, The Netherlands