INVASION DYNAMICS OF IMPATIENS-GLANDULIFERA - A CENTURY OF SPREADING RECONSTRUCTED

The invasion of Impatiens glandulifera in the territory of the Czech Republic, Central Europe, was reconstructed on the basis of floristic records. The first spontaneous occurrences were reported from the end of the 19th century. The exponential phase of invasion started in the 1930s and the highest increase in the cumulative number of localities reported occurred in the 1960s. Since its introduction, I. glandulifera has spread into 47.4% of available mapping squares. The species is closely confined to riparian habitats. At present it occupies 56% of the length of larger river systems. It is predicted that it will occur in all larger rivers in the Czech Republic by c. 2025, assuming that the rate of invasion remains constant. The rates of invasion in the Czech Republic, British Isles, Bavaria (Germany), and Slovakia are compared. In all the countries considered, the greatest increase occurred in recent decades, and was related to the date of escape from cultivation. Although the situation in the Czech Republic is at present not critical, the ability of I. glandulifera to outcompete native flora, and its predicted expansion along water courses, indicates that it could become a more serious threat to nature conservation in the future.