Factors limiting and promoting the invasion of Impatiens balfourii
Impatiens balfourii (Balsaminaceae) is native to the western Himalayas and has been introduced into the EPPO region as an ornamental plant species. The species has been cultivated in France, Great Britain and Italy since the early 20th century. The species has shown invasive tendencies in the EPPO region over the last 15 years and it is recorded as invasive in France, Italy and Croatia. Plant performance parameters in populations straddling the Swiss-Italian border were measured in different habitat types (ruderal areas, forest, roadside and stream habitats) along with natural enemy damage. In Italy, populations of I. balfourii were concentrated along roadsides, whereas in Switzerland the populations were located in ruderal areas, forest and stream habitats. Plant size differed significantly between all studied habitat types where the largest individuals were found along roadsides and the smallest were found along streams. Plant fecundity (expressed as seed weight and number of flowers) was highest in ruderal areas and lowest in forests. Leaf damage by natural enemies was lowest for plants growing along roadsides. There were no significant differences in terms of natural enemy damage between plants growing in other habitats.
Sources
Najberek K, Nentwig W, Olejniczak P, Krol W, Baś, Solarz W (2017) Factors limiting and promoting invasion of alien Impatiens balfourii in Alpine foothills. Flora 234, 224-232.