The materials to the "black book" of the flora of the Crimean Peninsula.
The "blacklist" of the Crimean flora, on the territory of two administrative units-the Republic of the Crimea and the federal city of Sevastopol-is presented. The analysis of the alien species of the Crimean flora was carried out and the alien species of higher plants most dangerous invasive for ecosystems were identified in accordance with the recommendations for keeping the Black Books. The data on distribution, habitats, and invasive status (IS) of 70 species are summarized. Transformers are represented by nine species with IS 1 (Ailanthus altissima, Bupleurum fruticosum, Elaeagnus angustifolius, Fraxinus ornus, Jacobaea maritima, Opuntia engelmannii subsp. lindheimeri, O. fragilis, O. humifusa, Rhamnus alaternus); they change the appearance of ecosystems. Nineteen alien species actively disperse and naturalize in disturbed seminatural and natural habitats (with IS 2), and 42 species (with IS 3) are widely distributed in disturbed habitats. The peculiarity and variety of soil and climatic conditions of the peninsula contribute to the penetration of alien species, many of which are invasive only in the territory of the Republic of the Crimea and the city of Sevastopol. This article is a necessary step toward the preparation of the Black Book of the flora of the Crimean Peninsula and the basis for making a decision on prevention of economic and environmental damage of the natural biodiversity of the region.