1. Department of Ecology; University of Kaiserslautern; D-67663 Kaiserslautern Germany
2. Department of Forest Ecology and Management; Swedish University of Agricultural Sciences; S-901-83 Umeå Sweden
3. Department of Statistical Science; Cornell University; Ithaca New York 14853 USA
4. GATC Biotech AG; European Genome and Diagnostics Centre; D-78467 Konstanz Germany