1. Long-term Ecology Laboratory, Oxford University Centre for the EnvironmentSouth Parks Road, Oxford OX1 3QY, UK
2. Leslie Hill Institute for Plant Conservation, Botany Department, University of Cape TownPrivate Bag X3, Rondebosch 7701, South Africa
3. Department of Botany, The Natural History MuseumCromwell Road, London SW7 5BD, UK