Neophyte plant species in hydrophilous flora of Baikal Siberia

Basing on the time of the first introduction, the adventive species are divided into two fractions - archeophytes and neophytes. In different regions, the time boundary separating these two groups differs. For example, in Western and Central Europe, species introduced in the region before the discovery of America, namely, before the year of 1500 are treated as archeophytes. All the species, introduced after this date, are neophytes. In the European part of Russia, such time border is the beginning of the XVI-th century for Central Chernozem region, the middle of the XVI-th century is for Vyatka-Kama region, the XVII-th century is for the Middle Urals and the beginging of the XVII-th century is for the Trans-Ural region. To separate archaeophytes and neophytes, the fractions of alien plants within the flora of Baikal Siberia, as a time boundary, I propose the middle of the XIX-th century (namely, the 1850th year). At this time, NS Turczaninow published his comprehensive flora of Baikal-Dahuria region, including 1402 numbered species and a number of unnumbered varieties. At present, many of these varieties are accepted as separate species. During the XIX-th century, the increasing of population in Baikal Siberia was gradual and not massive. The intensive settlement of the region started at the end of the XIX-th and in the beginning of the XX-th centuries, when the Trans-Siberian Railway was constructed. So, the Turczaninow's synopsis fixes the floristic situation before the intensification of the anthropogenic impact and introduction of a huge number of new adventive species in Baikal Siberia. Species introduced to the regional flora in the second half of the XIX-th century should be distinguished as neophytes. As an example, I accounted and analyzed neophytes in hydrophilous flora of Baikal Siberia. All the 14 hydrophilic neophytes (Typha laxmannii Lepech., Elodea canadensis Michx., Glyceria fluitans (L.) R. Br., G. plicata (Fries) Fries., Juncus tenuis Willd., Persicaria foliosa (Lindb. fil.) Kitag., Rorippa х armoracioides (Tausch) Fuss, R. austriaca (Crantz) Besser, R. sylvestris (L.) Besser, Lythrum salicaria L., L. virgatum L., Lycopus exaltatus L. fil., Stachys palustris L., Bidens cernuus L.) are accidentally introduced to the region during last century. Usually, every decade one or two species were introduced into the flora. Only in the 1950th were recorded three new species. Thus, a general increasing rate in introduction of adventive species into Baikal Siberian flora is not observed in its hydrophilous fraction. Ten neophyte species are recorded in Irkutsk Oblast, seven species - in the Republic of Buryatia and three species - in Zabaikalskii Krai. Typha laxmannii, a Central Asian species, is advenitive only in Irkutsk Oblast. Eight species are classified as naturalized ones and one species, Elodea сanadensis, is distinguished as invasive species. Most neophytes are originally European or European-West Siberian species.

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