1. Ecosystèmes Forestiers d'Afrique Centrale (ECOFAC), Box Postale 15115 Libreville, Gabon.
2. Department of Animal Biology, University of Barcelona, ES-08028 Barcelona, Spain.
3. Department of Evolutionary Biology, Uppsala University, SE-752 36 Uppsala, Sweden.
4. Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany.