1. Department of Soils, Federal University of Paraná, C. Postal 2959, 89.035‐050, Curitiba/PR, Brazil;
2. Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kitaku, Sapporo 060‐8589, Japan;
3. Present address: Japan International Research Center for Agricultural Sciences, 1–1 Ohwashi, Tsukuba 305‐8686, Japan;
4. Laboratory of Plant Systematics, Institute of Botany and Microbiology, K. U. Leuven, Kasteelpark Arenberg 31, B−3001 Leuven, Belgium;
5. Present address: Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK