One of the characteristic features of urban floras is their homogenization, synonymous with the loss of regionally unique species and reduction in functional diversity. In our work we examined the species composition of alien species in the flora of Russian cities to identify the contribution of this fraction to the homogenization and differentiation of urban floras. Alien species were classified into archaeophytes and neophytes according to the time of introduction (i.e., before or after 1800). The differentiation between the floras was quantified using the Simpson dissimilarity index. Archaeophytes reduce the beta-diversity of urban flora in the investigated region. Neophytes on the contrary contribute to the differentiation of the species composition of the studied urban floras. Species similarity of urban flora depends on the distance between cities – the more is the distance between cities, the lower is their species similarity.

A.S. Tretyakova, B.N. Yakimov, O.G. Baranova, S.A. Senator, Ya.M. Golovanov, E.N. Bralgina