Patterns of Secondary Range Formation for Heracleum sosnowskyi and H. mantegazzianum on the Territory of Russia

A map of the current distribution of Heracleum sosnowskyi Manden. on the territory of Russia was composed. It reflects the space and time dynamics of the widening of the secondary range of the weed including the data on the territories not favorable for its invasion. It was shown that intentional introduction was of the main importance in the modern formation of the secondary range of the weed. It led firstly to local distribution of the plant in agricultural areas in a few regions of the Soviet Union, which were the centers of cultivation of this plant as a fodder crop, and further to "escapement from culture" and distribution of the plant initially near the centers of its cultivation and then to uncontrolled widening of the invasive range of Heracleum sosnowskyi. The species is still more associated with synanthropic habitats than natural ones and forms monospecific thickets on large areas. It was noted that another species of the giant hogweeds-Heracleum mantegazzianum-was also intentionally introduced in the territory of Russia, although to a significantly lesser degree.