1. Department of BiologyDuke University Durham, North Carolina 27708‐0338 U.S.A.
2. Instituto de BiologíaUniversidad Nacional Autónoma de México (UNAM) C.P. 04510 Mexico City Mexico
3. UBC HerbariumBeaty MuseumUniversity of British Columbia Vancouver British Columbia V6T1Z4 Canada
4. Life Science SchoolNingxia University Yinchuan, Ningxia Hui Autonomous Region 750021 China
5. Department of Ecology and Evolutionary BiologyUniversity of Connecticut Storrs, Connecticut 06269‐3043 U.S.A.
6. Evolution and Conservation BiologyUniversity of Liège Sart Tilman B22 4000 Liège Belgium
7. Botanical MuseumFinnish Museum of Natural HistoryUniversity of Helsinki P.O. Box 7 00014 Finland
8. Both authors are last authors for this publication and are listed here in alphabetical order Author