1. Department of Geography; University of Toronto Mississauga; 3359 Mississauga Road Mississauga Ontario L5L 1C6 Canada
2. Department of Biology; University of Toronto Mississauga; 3359 Mississauga Road Mississauga Ontario L5L 1C6 Canada
3. Department of Crop Sciences, Agroecology; University of Göttingen; Grisebachstrasse 6 Göttingen 37077 Germany
4. Biodiversität der Pflanzen; Technische Universität München; Maximus-von-Imhof Forum 2 Freising 85354 Germany
5. Department of Biology; Imperial College at Silwood Park, Ascot; Berkshire SL5 7PY UK