1. Dept of Physics, Chemistry and Biology, Div. of Theoretical Biology; Linköping Univ.; SE-58183 Linköping Sweden
2. Research Centre for Systems Biology, Univ. of Skövde; PO Box 408, SE-541 28 Skövde Sweden
3. Weierstrass Inst.; Mohrenstr. 39 DE-10117 Berlin Germany
4. Environmental Research Inst., Univ. College Cork; Lee Road Cork Ireland
5. School of Biological Sciences, Queen's Univ. Belfast; 97 Lisburn Road Belfast BT9 7BL UK
6. Dept of Ecology; Swedish Univ. of Agricultural Sciences; Box 7044, SE-750 07 Uppsala Sweden