1. Department of Ecology and Evolutionary Biology; University of Tennessee; Knoxville Tennessee 37996 USA
2. Nature Conservation and Plant Ecology; Wageningen University and Research Centres; 6700 AA Wageningen The Netherlands
3. Department of Biology; Indiana University; Bloomington Indiana 47405 USA
4. Department of Terrestrial Ecology; Netherlands Institute of Ecology (NIOO-KNAW); 6700 AB Wageningen The Netherlands
5. Laboratory of Nematology; Wageningen University and Research Centre; 6700 ES Wageningen The Netherlands