1. The Center for African Area Studies, Kyoto University, 46, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, Kyoto, Japan
2. Department of Forest Science and Resources, Nihon University College of Bioresource Science, 1866, Kameino, Fujisawa, Kanagawa, Japan
3. Institut de Recherche en Écologie Tropicale, Centre National de la Recherche Scientifique et Technologique (IRET–CENAREST), B.P. 13354, Libreville, Estuaire, Gabon