The first comprehensive multilocus phylogeny of the lichenized genus <i>Micarea</i> (Ectolechiaceae, Ascomycota)

Abstract Micarea is a crustose cosmopolitan lichen genus that belongs to the euascomycete class Lecanoromycetes. Recent molecular phylogenies on the genus based on one to three loci have mostly focused on Micarea s.str., including the type species M . prasina , and suggested that Micarea s.l. is paraphyletic. The remainder of the genus remains more poorly studied, and infrageneric delimitations and the phylogenetic position of many taxa are still insufficiently known. The aim of this study is to generate, for the first time, a multilocus phylogeny for Micarea that includes all the main lineages in order to assess phylogenetic relationships in the genus. We specifically examine whether Micarea is monophyletic and whether a broader sampling and the addition of further gene regions can increase the resolution and support in the backbone, and result in a more resolved and better‐supported phylogeny of Micarea as a whole. The phylogeny of Micarea was reconstructed using five loci (mtSSU rDNA, Mcm7 , nuITS rDNA, RPB1 , RPB2 ) from a worldwide sample of 314 Micarea specimens representing 102 species. 970 new sequences were produced for this study, including molecular data from 18 previously unsequenced species. In the combined analyses, Micarea s.l. is resolved as a monophyletic group if Fellhaneropsis and Szczawinskia are included, and consists of several strongly supported clades. Furthermore, Micareopsis is included in Micarea based on the separate phylogeny of the Mcm7 dataset. We discuss different alternatives to classify the clades and consider the mesogeneric approach as the currently most reasonable taxonomic solution, i.e., to treat the clade containing M. crassipes and relatives, the sister clade to the rest of Micarea , as a separate genus under the name Helocarpon , and to include the remaining clades in the genus Micarea . We reduce Szczawinskia to synonymy with Micarea but conclude that more data are needed to resolve the status of Fellhaneropsis and Micareopsis . Despite morphological and chemical variation, the infrageneric clades can often be characterized by a combination of several phenotypic characters, including thallus structure, ascospore and conidial morphology, and the occurrence of different pigments and secondary substances. Some of the characters are exclusive (such as the secondary substances methoxymicareic acid, prasinic acid, and micareic acid) or almost so (goniocyst thallus structure) for the core group of the genus, i.e., the M . prasina clade. Our study shows that the genus contains as yet undescribed diversity. Four lineages are described as new species: Micarea arthonioides , M. athromelaena , M. lignosorediata and M. regalis .