The result of cluster analysis was the cross-classification of sites and species given in S1 Table, where the groups of sites A, B and C (Fig 2) and the groups of species 1, 2, 3, and 4 (Fig 3) were recognized. The similarity structure of the data was improved by highlighting central species in bold and nuclear species underlined. The sites belonging to groups A (three sites) and B (eight sites) are in the region of the deciduous forests, while the sites belonging to group C (six sites) are in the region of evergreen Mediterranean forests.