1. Laboratory of Plant Biology and Ecology, Department of Plant Biology and Physiology, UFR/SVT, University of Ouagadougou, 03 BP 7021 Ouagadougou 03, Burkina Faso
2. Department of Ecology and Geobotany, Institute for Ecology, Evolution and Diversity, J. W. Goethe University, Max-von-Laue-Str. 13, Hauspostfach 19, 60438 Frankfurt am Main, Germany