1. Department of Botany, National Museum of Nature and Science, Amakubo 4-1-1, Tsukuba, Ibaraki 305-0005, Japan
2. Botanic Garden, Field Science Center for Northern Biosphere, Hokkaido University, Sapporo, Hokkaido 060-0003, Japan
3. Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Japan
4. Laboratory of Ecology and Systematics, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan
5. Department of Education, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan