1. Key Laboratory of Plant Resources Conservation and Sustainable Utilization; South China Botanical Garden; the Chinese Academy of Sciences; No 723 Xingke Road Tianhe District Guangzhou 510650 China
2. College of Horticulture; South China Agricultural University; Guangzhou 510642 China
3. Department of Botany; MRC-166; National Museum of Natural History; Smithsonian Institution; P.O. Box 37012 Washington DC 20013-7012 USA