1. Field Science Center, hokkaido University, Kita 11, Nishi 10, Sapporo 060-0811, Japan
2. Department of General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo 153-8902, Japan
3. Animal Biology Division, Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños, College, Laguna 4031, Philippines
4. Tohoku Research Center, Forestry and Forest Products Research Institute, Nabeyashiki, Morioka 020-0123, Japan
5. School of Biological Sciences, Tokai University, Minamisawa, Sapporo 005-0825, Japan