The dynamics of the taxonomic composition of the alien fraction of the urban flora in the Kyiv urban area, Ukraine

This article presents the results of an investigation into the recent taxonomic composition of the alien fraction of the urban flora in the Kyiv urban area (KUA). Its main dynamic tendencies over the last 20 years have been highlighted, along with the most probable phytoinvasive threats. The obtained linear regression equation allowed forecasting for the growth in the abundance of alien plant species against the background of the enlargement of the Kyiv urban area (r=0.53) and its human population numbers (r=0.87). The alien fraction of the urban flora of the KUA contains 717 taxa of vascular plants (668 species, 41 subspecies, 6 varieties, 1 form and 1 nothoform). In the past 20 years, the number of species of the urban flora of the KUA has increased by at least 166 alien taxa, some of which are representatives of new genera, families, and orders for our flora. This enrichment of the taxonomic structure of the alien fraction in the urban flora of the KUA has caused changes in the ratio of life forms, ecotypes, invasiveness of species, and other features. We specified probable invasive threats, conditioned by the formation of the group of new woody species, hydrophytes capable of rapidly accumulating their phytomass, some genera complexes involving alien and local species, which are inclined to hybridization.