1. Ecology & Biodiversity Institute of Environmental Biology Utrecht University Padualaan 8 3584 CH Utrecht the Netherlands
2. Department of Bioscience Aarhus University Vejlsøvej 25 P. O. Box 314 DK‐8600 Silkeborg Denmark
3. Plant Ecophysiology Institute of Environmental Biology Utrecht University Padualaan 8 3584 CH Utrecht the Netherlands