1. Institute of Mathematics, Statistics and Actuarial Sciences, University of Kent, Canterbury, Kent, CT2 7NF, England
2. Centre d'Ecologie Evolutive et Fonctionnelle, Centre National de la Recherche Scientifique UMR 5175, 1919 Route de Mende, 34293 Montpellier, Cedex 5, France
3. Centre for Research into Ecological and Environmental Modelling, University of St Andrews, St Andrews, The Observatory, Buchanan Gardens, KY16 9LZ, Scotland
4. Institute of Cell, Animal and Population Biology, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh EH9 3JT, Scotland
5. Percy FitzPatrick Institute, Department of Science and Technology Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
6. Department of Biological Sciences, University of Tulsa, Tulsa, Oklahoma 74104
7. Department of Tourism, Environment and Conservation, Private Bag X6102, Kimberley 8300, Northern Cape, South Africa