Tidying up the genusLetharia: introducingL. lupinasp. nov. and a new circumscription forL. columbiana

Abstract

AbstractWestern North America is the global centre of diversity forLetharia, a distinctive and cryptically diverse genus of lichenized fungi belonging to theParmeliaceae. The genus is characterized by a shrubby, fruticose habit and presence of vulpinic acid. Previous studies using multiple fungal nuclear loci revealed the existence of two distinct species-level lineages within the traditional concept ofL. vulpinaand four such lineages withinL. columbiana. Here we use molecular sequence data in an attempt to settle long-standing taxonomic issues in the genus. Our results confirm the widespread existence withinL. vulpinas. lat. of two distinct species-level groups, each forming a mutually exclusive partnership with a separate algal clade withinTrebouxia jamesiis. lat. Accordingly, we formally describe the segregate speciesL. lupinasp. nov. Our results also support the evolutionary independence of four candidate species previously circumscribed fromL. columbianas. lat. One of these lineages,L.‘gracilis’, has already received species recognition asL. gracilis, while a second,L.‘lucida’, is epitypified here againstL. columbianas. str. Based on results from species delimitation analyses under the multispecies coalescent model, the two remaining lineages,L.‘barbata’ andL.‘rugosa’, also warrant formal taxonomic recognition; however, we refrain from describing these species pending additional studies of diagnostic characters, ecological preference, and distributions.