1. Research Institute of Mechanics and Applied Mathematics, Department of Mathematical Modelling in Ecology and Economics, Rostov State University, Stachki St. 200/1, 344104 Rostov‐on‐Don, Russia;
2. Institut national agronomique Paris‐Grignon, 75231 Paris cedex 05, France; and
3. Écologie des populations et communautés, Bât. 362, Université Paris‐Sud XI, 91405 Orsay cedex, France