Polygonum ramosissimum Maxim. (Polygonaceae Juss.) as a new adventive species in Siberia

One of the ways to replenish species composition of the flora of a defined territory is bringing species from other regions. Polygonum ramosissimum Michx. is a North American plant that lives on sandy beaches and saline soils (Britton, Brown, 1970; Costea et al., 2005). The species was found in Eastern Europe at the end of the last century and among the adventive plants of Moscow, Moscow and Leningrad regions (Ignatov, 1990; Tsvelev, 1996, 2012) and also in Ukraine (Mosyakin, Fedoronchuk, 1999) at the beginning of the present one. P. ramosissimum is characterized by a broad intraspecific variation, there are a number of forms and two subspecies, which differ in leaf color, shape of the tops of leaves and the presence or absence of heterophylly. In addition, the plants belonging to this species vary in color of the edges of the parts of a perianth (yellowish, whitish, rarely pink), the nature of the fetus (shiny or matt, smooth or knobby), its size relative to a perianth (if it is enclosed in a perianth or sticks out of it) and even the size of leaves at the upper part of shoots which are sometimes so small that are not bigger than flowers. M. Costea et al. (2005) point to these signs, separating this species from others in their identification way five times. When studying the flora of Tyumen oblast in the field seasons of 2006-2011, there was collected the material, whose species identification definition made it possible to identify it with P. ramosissimum. Herbarium specimens are stored in the main collection of I.V. Kuzmin (Tyumen), doublets - in the Herbarium of V.P. Astafiev Krasnoyarsk State Pedagogical University (KRAS). The plants of the Siberian population have well-developed leaves at the top of the shoots, much bigger than the flowers, which does not allow bringing together the species with P. bellardii All. from the subsection Patula Tzvel. of the typical section, as it was done by Costea et al. (2005). The molecular-phylogenetic studies based on the study of nucleotide polymorphism ITS1-2 of nuclear rDNA showed that P. ramosissimum can be isolated in a special section in conjunction with other North American species P. buxiforme Small, P. achoreum S.F. Blake, or they can be included in the sample section (Yurtseva et al, 2008). The species is similar to P. aviculare L., which is confirmed by N.N. Tsvelev (1996, 2012), who placed these species near in the key and put them in one (typical) subsection. P. ramosissimum herbarium, collected in five administrative districts of Tyumen oblast, located in different natural zones (southern taiga, subtaiga and the transitional zone between them), and even in different years in the Vagaysky district, in our point of view, shows the naturalization of this species in Western Siberia. The habitats of P. ramosissimum along the roadsides give a reason to assume its more wide-spread occurrence in Tyumen oblast and expansion in other regions of Siberia. Key words: Polygonum; Polygonaceae; West Siberia.

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