The study of the ranges, habitats and current state of rare and threatened species of plants is a relevant task of ecological research. The paper presents the results of the study of habitats and current state of populations of two rare species of Ukrainian flora Aconitum lasiocarpum (Rchb.) Gáyer and A. variegatum L. (Ranunculaceae) in the lowlands of Ukraine. These species are members of the mountain element of the flora of lowlands of Ukraine and glacial relics, which descended from the Carpathians Mountains to the lowlands of Ukraine during glaciation. Aconitum lasiocarpum is a rare species of European flora, included to the Red Data Books of the Czech Republic and Slovakia, Poland and Ukraine. Unlike the well studied A. lasiocarpum populations in the main part of the range in the Carpathian Mountains, local populations of this species near the eastern limit of the range in the lowlands of Ukraine remain undescribed. In these exclaves of the range in the lowlands of Ukraine A. lasiocarpum is a glacial relic. Here it grows in alder forests Ribo nigri-Alnetum ordo Alnion glutinosa alliance. Lowland A. lasiocarpum populations consist of 1000–10000 adults with a significant number of young individuals. In the past lowland A. lasiocarpum populations occupied a much large area. Deforestation and drainage melioration led to reduction of the populations. Taking into account the low number of glacial relic populations at the eastern limit of the range of A. lasiocarpum, all localities of this species in the lowland part of the range in Ukraine must be taken under protection in situ. Aconitum variegatum L. grows in wet alder and oak forest and in areas with hazel shrubs. The populations of this species in lowlands of Ukraine occupy a very small area and are characterized by low numbers of individuals. In the past populations of this species in the lowlands of Ukraine occupied a larger area. As a rare species of the Ukrainian flora A. variegatum deserves to be included to the Red Data Book of Ukraine. We propose to protect the unique population of A. variegatum near Susk village in Rivne region as a botanical reserve.

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