1. Department of Systematics and Evolutionary Botany, University of Zurich , Zurich 8008 , Switzerland
2. Department of Botany, University of Wyoming , Laramie 82071 , USA
3. Department of Biology, University of Fribourg , Fribourg 1700 , Switzerland
4. Department of Biological and Environmental Sciences and Global Gothenburg Biodiversity Centre, University of Gothenburg , Gothenburg SE-405 30 , Sweden
5. Swiss Institute of Bioinformatics , Fribourg 1700 , Switzerland