The Commander Islands as a hotspot for <i>Teloschistales</i> diversity in the North Pacific: a meeting point for different lichen biotas

Abstract Using a combination of field inventories in temporary sample plots and extensive molecular analyses, the diversity of lichens in the order Teloschistales on the Commander Islands (Kamchatka Territory, Russia) was assessed. Nearly 600 specimens of the order were collected from 154 sample plots, which included 36 species, one belonging to the family Brigantiaeaceae and the rest to the Teloschistaceae ; of these, 18 species belonged to the subfamily Caloplacoideae and 17 to the Xanthorioideae. The diversity of the Teloschistales is unevenly distributed across the different habitat types of the archipelago, namely coastal, tundra and floodplain. Each habitat type has a specific lichen composition and a combination of traits. Coastal habitats have the highest number of species and the greatest number of species per plot. The Commander Islands are characterized by having the highest number of Teloschistales species when compared with the most well-studied local biotas in the North Pacific. This is probably due to the presence in the archipelago of species with diverse distribution patterns, including western North American species, North-East Asian species, and endemic species, as well as species more widely distributed in the arctic-alpine and boreal regions of both Asia and North America. The putative role of the Commander and Aleutian Islands in migrations of lichens between Asia and North America is discussed. ‘ Caloplaca ’ litoricola and Polycauliona flavogranulosa from the Commander Islands and Orientophila corticola from the southern part of the Russian Far East are new to Russia. Three species are proposed as new to science: Athallia subrotundispora (epilithic or epiphytic lichen characterized by an inconspicuous thallus and widely ellipsoid to subglobose ascospores, 14–16(18) × 10–11 μm, with septa 6–7 μm wide), Gyalolechia orientoinsularis (corticolous lichen characterized by a yellow thallus and apothecia with a yellow to orange true exciple highly contrasting with a brown to reddish brown disc) and G. paradoxa (muscicolous or lichenicolous lichen characterized by an orange to orange-red thallus and ellipsoid to widely ellipsoid and subglobose ascospores, 12–19 × 8–13 μm, with septa 4–9 μm wide). Lendemeriella kamczatica , L. phaeocarpella and Polycauliona etesiae are new combinations. A lichenicolous morph of Lendemeriella tornoënsis is reported for the first time and a key to species of Gyalolechia s. lat. occurring in the Far East is provided.