1. The New York Botanical Garden, Science Division, Bronx, NY 10458, USA
2. The Graduate Center, City University of New York, Biology Program, 365 Fifth Ave, New York, NY 10016, USA
3. Yale University, School of Forestry and Environmental Studies, 195 Prospect Street, New Haven, CT 06511, USA
4. McGill University, Department of Biology, 1205 Dr Penfield Avenue, Montreal, QC, Canada H3A 1B1