1. Department of Ecology and Evolutionary Biology; Princeton University; Princeton New Jersey 08544
2. Santa Fe Institute; Santa Fe New Mexico 87501
3. Centre for Mathematics and the Environment; University of Exeter; Penryn Campus Cornwall United Kingdom
4. Laboratoire de Probabilités et Modèles Aléatoires des Universités Pierre et Marie Curie et Denis Diderot; Paris France
5. Collège de France; Center for Interdisciplinary Research in Biology CNRS UMR 7241; Paris France