1. 1 Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 2 Gagarin St., 1113 Sofia, Bulgaria; cmdenchev@yahoo.co.uk
2. 2 AG Geobotanik, Ruhr-Universität Bochum, ND 03, Universitätsstr. 150, 44801 Bochum, Germany; e-mail: martin.kemler@rub.de; dominik.begerow@rub.de