New and Rare Vascular Plant Species of the Kuril Islands: Distribution, Ecology, and Population Status

Despite the long history of floristic studies of the Kuril Islands, the central part of the Kuril archipelago, particularly Urup Island, remains poorly studied. The question of the position of Urup Island in the biogeographic and floristic subdivision systems is controversial, which seems to be due to unsufficient floristic data. Studies carried out by the authors in 2019 on the islands of Urup and Iturup provided new data about the distribution, habitats, and population status of 28 indigenous species of vascular plants, including 14 species listed in the Red Data Book of the Russian Federation (2008) and the Red Data Book of the Sakhalin Oblast (2019). Myriophyllum ussuriense was first discovered in the Sakhalin Oblast and recommended for inclusion into the regional list of rare vascular plant species and the Red Data Book of the Sakhalin Oblast. Four species (Corallorhiza trifida, Pedicularis adunca, Salix arctica, and S. chamissonis) were first revealed in the southern Kuril Islands. In addition, eight species (Carex livida, Eleocharis margaritacea, Epipactis papillosa, Juncus articulatus, J. decipiens, Neottia puberula, Poa austrokurilensis, and Utricularia minor) were first found on Urup Island. Occurrence of four species (Isoëtes asiatica, Hydrangea petiolaris, Rhynchospora alba, and Salix fuscescens) on Urup Island was confirmed by new records. The data obtained confirm that Urup Island takes an intermediate position in the floristic subdivision of the Kuril archipelago and represents a transitional zone between the northern and southern Kuril Islands, which is significantly enriched by “southern” East Asian species.