A new lichen and lichenicolous fungus from <i>Larix laricina</i> in patterned fens of boreal North America

Abstract Calicium poculatum and Ramboldia canadensis are described as new species occurring on Larix laricina . Calicium poculatum , currently known from four Canadian provinces and the US state of Minnesota, is characterized by its short-stalked black ascomata, short ascospores and occurrence as a parasite on Lecanora caesiorubella subsp. saximontana . Based on DNA sequence data, its nearest relative is the likewise parasitic Calicium episcalaris . Ramboldia canadensis , currently known only from dead wood of Larix laricina snags in Canada, engages in a fully developed lichen symbiosis with Trebouxia simplex and is characterized in statu symbiotico by having a rimose to verrucose-areolate, greyish creamy sorediate thallus with dark brown to blackish soredia that begin on the margins, and the occurrence of a secondary metabolite similar to barbatolic acid. Phylogenetic analysis recovers it as sibling to a clade of the genus heretofore known only from the Southern Hemisphere and the lower latitudes of the Northern Hemisphere. We also report Lecidella xylophila as new to North America.