1. Department of General Systems Studies University of Tokyo 3‐8‐1 Komaba Meguro Tokyo153‐8902 Japan
2. Department of Ecology and Ecosystem Modelling Institute of Biochemistry and Biology University of Potsdam Am Neuen Palais 10 Potsdam 14469 Germany
3. Department of Biology Ithaca College 953 Danby Rd. Ithaca NY14850 USA