1. CEFE‐CNRS, UMR 5175, Equipe Interactions Biotiques, 1919 Route de Mende, 34 293 Montpellier Cedex 5, France;
2. Author for correspondence: tel +33(0)607 1234 18; fax +33(0)4 67 41 21 38;)
3. Institute of Botany, Academy of Sciences of the Czech Republic, Lesní 323, 252 43, Průhonice, Czech Republic;
4. Department of Plant Physiology, Charles University in Prague, Viničná 5, 128 44, Prague, Czech Republic;
5. EcoLab, Laboratoire d’écologie fonctionnelle, UMR 5245 CNRS, Université de Toulouse, INPT, 29 rue Jeanne Marvig, 31055 Toulouse Cedex, France (