[1] Smithsonian Inst, Dept Bot, Natl Museum Nat Hist, Washington, DC 20013 USA
[2] Beijing Forestry Univ, Sch Ecol & Nat Conservat, Beijing 100083, Peoples R China
[3] Chinese Acad Sci, Inst Bot, State Key Lab Systemat & Evolutionary Bot, Beijing 100093, Peoples R China
[4] Chinese Acad Sci, Inst Bot, Ctr Documentat & Informat Management, Beijing, Peoples R China