The lichens of Sommers (Leningrad Region, Russia) — a case study of biodiversity on a small remote island in the Gulf of Finland

The paper is dedicated to lichens and allied fungi of Sommers Island. The revealed lichen diversity has a total of 183 species, including 176 lichenized, six lichenicolous fungi, and one non-lichenized saprobic fungus. Umbilicaria subpolyphylla is new to the North-West of European Russia and Protoparmeliopsis achariana is firstly reported for the Leningrad Region. Seven species discovered on Sommers are listed in the Red Data Book of the Leningrad Region; they are mostly connected with exposed rocky habitats. Despite the small size of the island, the revealed lichen biota is rich and worth protecting.