Checklist of lichens of Shikotan Island (Southern Kuril Islands, Russian Far East)

. Information on lichens of Shikotan Island based on original and literature data is provided. Altogether 278 lichen species and allied fungi are documented, of which Xylographa hians is new to Eurasia, Candelariella subdeflexa is new to Russia, nine species are new to the Russian Far East, 28 species are new to the Sakhalin Region, 39 species are new to Kuril Islands

Shikotan Island is characterized by low mountainous and hilly terrain. The main heights range from 170 to 240 m a. s. l. The highest peak of the island is Mount Shikotan with a height of 405 m, located on its northern tip (Yuzhnye…, 1992). The climate of Shikotan is temperate maritime, influenced by the monsoons. Precipitation falls on average 1240 mm per year. The southeastern coast of the island has a cooler and more humid climate than the northwestern coast which is associated with the influence of the cold Kuril Current and the warm Soya Current on the coasts (Khomenko, 2003). Forests occupy about 23% of the island. Dark coniferous forests formed by spruces [Picea yezoensis (Siebold et Zucc.) Carrière, P. glehnii (F. Schmidt) Mast.] and fir (Abies sachalinensis F. Schmidt) predominate, in some places there are birch (Betula ermanii Cham.) forests and fragmentary larch (Larix kurilensis Mayr) sparse forests. Yew (Taxus cuspidata Siebold et Zucc. ex Endl.) and cork tree (Phellodendron amurense Rupr.) also take part in the forest stand. The river valleys and floodplains are dominated by alder [Alnus hirsuta (Spach) Rupr.] forests and willow communities with the participation of rowan (Sorbus commixta Hedl.) and maple species. Most of the island is treeless, apparently due to logging and fires in the past, the vegetation is dominated by Sasa kurilensis (Rupr.) Makino et Shibata (Yuzhnye…, 1992;Khomenko, 2003;Grishin, 2008).
The aim of this paper is to summarize all information on lichens of Shikotan Island based on original and literature data.

Materials and Methods
The lichen specimens presented in the paper were collected by authors in Shikotan Island in June 2017. Most of the collections were made in the southwestern and northeastern parts of the island (Malye Kurily Reserve) ( Fig. 1) mainly in various types of forest, but also on coastal rocks and rock outcrops in the interior of the island (Fig. 2). In total, we collected about 1200 specimens and determined about 800 of them. All geographical coordinates are given in the coordinate system WGS 1984. The herbarium of the Sakhalin branch of the Botanical Garden-Institute of the Far Eastern Branch of the Russian Academy of Sciences, where S. I. Tchabanenko worked, is currently not available for revision. Therefore, a revision of specimens from the Shikotan Island was carried out in the Herbarium of the Komarov Botanical Institute of the Russian Academy of Sciences (LE). The laboratory study was carried out according to the standard technique (The Lichens…, 2009) in the Laboratory of Lichenology and Bryology of Komarov Botanical Institute using a binocular stereoscopic microscope MSP 1 var. 2, transmitted light microscope Zeiss Primo Star, a standard set of chemical reagents for carrying out color spots reactions for identification of certain groups of lichen substances in thalli. The nomenclature of lichens mainly follows Yoshimura (1971), Elix, Hale (1987), Printzen, Tønsberg, (2003), Blanco et al. (2004), Frisch et al. (2006, Westberg (2007), Spisok… (2010), Spribille et al. (2014), Gagarina (2015), Mongkolsuk et al. (2015), Printzen et al. (2016), Lendemer, Harris (2017), Sheard et al. (2017), , Westberg et al. (2021), and Flora… (2022).
All collected and identified specimens are stored in the herbaria of the Laboratory of Lichenology and Bryology, Komarov Botanical Institute (LE), Botanical Garden-Institute of the Far Eastern Branch of the Russian Academy of Sciences (VBGI), Polar-Alpine Botanical Garden-Institute of the Kola Science Centre of the Russian Academy of Sciences (KPABG).
Although forests occupy only about 23% of the island, they are the main source of lichen diversity (about 53% of lichens are represented by corticolous and lignicolous species). Most of the island is treeless and is not available for lichen colonization, due to the continuous cover of Sasa kurilensis and tall herb cover. Exceptions are seaside cliffs and rocky outcrops within the island, where there are enough microniches free from vegetation. To such habitats the remaining groups of lichens (saxicolous, terricolous, muscicolous) are confined. Thus, the lichen flora of Shikotan Island can be characterized as boreal involving tropical and subtropical species.
Among the South Kuril Islands, Shikotan Island ranks third in area (260 km 2 ), significantly behind Iturup (3187 km 2 ) and Kunashir (1490 km 2 ) islands. In addition, the Iturup and Kunashir islands are more than 70% occupied by forests. However, Shikotan Island is not inferior in the number of identified lichen species (278) to the Iturup (223) and Kunashir (373) islands. This is due to the different accessibility of the islands for researchers. Thus, lack of roads, difficult-to-pass Sasa kurilensis thickets on the Iturup Island make large areas inaccessible for research, therefore most lichen collections were made in the central and southern parts of the island. Kunashir and Shikotan are more accessible to researchers.