Botrychium virginianum (Ophioglossaceae), a new species for the flora of Volyn Polissia (Ukraine)

During floristic surveys conducted in the southern part of Volyn Polissia (Rivne Region) in July 2021, a rare and relict species, Botrychium virginianum (Ophioglossaceae), was discovered for the first time in this area. According to the Ukrainian sozological data, the species is included in the category Endangered; using the IUCN categorization, it is considered as a Critically Endangered (CR) species of the flora of Ukraine. In Ukraine, where the southern border of the species range is located, 30 localities have been recorded until present, most of them prior to the first half of the 20th century. The reported location of B. virginianum is associated with the carbonate uplift of the first floodplain terrace of the right bank of the Horyn River within the boundaries of the Kostopil-Berezniv physiographic district of Volyn Polissia. A small local population consists of at least five individuals with high vitality. The ecological and phytocenotic conditions of the reported species habitat have been studied and its limiting factors have been clarified. It is recommended to include this site with a cluster of rare species of the flora in the Suskyi Botanical Reserve of national importance, which is located nearby.