Invasive Activity of Woody Plants in Tsytsyn Main Botanical Garden, Russian Academy of Sciences

The object of this study is the arboretum of Tsytsyn Main Botanical Garden, Russian Academy of Sciences, which was founded in 1945. The invasive activity is extremely low here: the arboretum collection currently includes 66 taxa of 35 genera belonging to 22 families (5% of the collection fund) of self-seeding or clonal woody plants that have a capacity for further naturalization in the Main Botanical Garden (MBG) of the Russian Academy of Sciences. The highest rates of naturalization were recorded for the species of the families Juglandaceae and Rosaceae, the fruits of which are dispersed by zoochoria. The greatest capacity for naturalization (5.3%) was demonstrated by plants that naturally grow in Europe, while plants growing in Asia (3.4%) and North America (3.0%) have lower naturalization. Only 15 intentionally introduced species (1.1% of the collection fund) were found outside the arboretum in natural cenoses that survived in the Main Botanical Garden of the Russian Academy of Sciences. Some seedlings have intermediate features between collection species and seem to be hybrids. It is concluded that, contrary to the published data, botanical gardens are not a direct vector for the invasion of alien species. Although many invasive species emerged in other regions of the world outside their natural range owing to intentional introduction, their invasion into natural communities should be associated with their further massive cultivation rather than with primary introduction.