Development of invasive weeds Ambrosia artemisiifolia L. and A. trifida L. (Asteraceae) in Moscow Oblast.
New data on the structure of seedlings, juvenile, immature, virginal, and generative individuals of invasive species Ambrosia artemisiifolia L. and A. trifida L. and the time of their transition to different age stages in Moscow and Moscow oblast have been obtained. These data can help in recognition of plants at different stages of their ontogenesis in nature and in their timely control. It has been shown that both species have a high germination rate; however, the pace of development differs, which affects the time of flowering and fruit ripening. For A. artemisiifolia, the duration of the growing season in Moscow and Moscow oblast is not enough to form mature seeds, while A. trifida in these conditions sets high-grade fruits and seeds with high germination capacity. The main propagation path of A. artemisiifolia fruits from the southern regions to the north is the railways. Seed drift of A. trifida is mainly associated with wheeled transport and transport and processing of grain. It has been suggested that A. trifida can potentially be a rather dangerous plant for the northeastern regions of Central Russia as an invasive species, which in the case of massive introduction of diaspores can occupy large areas in disturbed and natural communities and form stable self-renewing populations. The northward movement of A. artemisiifolia is more problematic. However, in consideration of wide adaptive potential of the species, including the shortening of development cycle and the formation of early maturing and female forms, it can be concluded that naturalization of the species in the northeastern regions of Russia is also possible.