1. Department of General Systems Studies; Graduate School of Arts and Sciences; University of Tokyo; 3-8-1 Komaba Tokyo 153-8902 Japan
2. School of Biological Sciences; Centre for Biodiversity and Conservation Science; The University of Queensland; St Lucia QLD 4072 Australia
3. Evolutionary Demography Laboratory; Max Planck Institute for Demographic Research; Rostock DE-18057 Germany