1. Instituto de Recursos Naturales y Agrobiologı́a de Salamanca (IRNASA-CSIC), Apdo. 257, 37071 Salamanca, Spain
2. Department of Physics, Norwegian University of Science and Technology, N-7491
Trondheim, Norway
3. Biology
Centre ASCR and Faculty
of Sciences, University of South Bohemia, Branišovská 31, 370 05 České Budějovice,
Czech Republic