Micareic acid

Six new Micarea species are described from Europe. Phylogenetic analyses, based on three loci, i.e. mtSSU rDNA, Mcm7 and ITS rDNA and ancestral state reconstructions, were used to evaluate infra-group divisions and the role of secondary metabolites and selected morphological characters on the taxonomy in the M. prasina group. Two main lineages were found within the group. The Micarea micrococca clade consists of twelve species, including the long-known M. micrococca and the newly described M. microsorediata, M. nigra and M. pauli. Within this clade, most species produce methoxymicareic acid, with the exceptions of M. levicula and M. viridileprosa producing gyrophoric acid. The M. prasina clade includes the newly described M. azorica closely related to M. prasina s.str., M. aeruginoprasina sp. nov. and M. isidioprasina sp. nov. The species within this clade are characterised by the production of micareic acid, with the exception of M. herbarum which lacks any detectable substances and M. subviridescens that produces prasinic acid. Based on our reconstructions, it was concluded that the ancestor of the M. prasina group probably had a thallus consisting of goniocysts, which were lost several times during evolution, while isidia and soredia evolved independently at multiple times. Our research supported the view that the ancestor of M. prasina group did not produce any secondary substances, but they were gained independently in different lineages, such as methoxymicareic acid which is restricted to M. micrococca and allied species or micareic acid present in the M. prasina clade.

Micarea is a lichenized genus in the family Pilocarpaceae (Ascomycota). We studied the phylogeny and reassessed the current taxonomy of the M. prasina group. We focused especially on the taxonomic questions concerning the type species M. prasina and, furthermore, challenges concerning type specimens that are too old for successful DNA barcoding and molecular studies. The phylogeny was reconstructed using nuc rDNA internal transcribed spacer region (ITS1-5.8S-ITS2 = ITS), mitochrondrial rDNA small subunit (mtSSU), and replication licensing factor MCM7 gene from 31 species. Fifty-six new sequences were generated. The data were analyzed using maximum parsimony and maximum likelihood methods. The results revealed four undescribed, well-supported lineages. Three lineages represent new species described here as M. fallax, M. flavoleprosa, and M. pusilla. In addition, our results support the recognition of M. melanobola as a distinct species. Micarea fallax is characterized by a vivid to olive green thallus composed of aggregated granules and whitish or brownish apothecia sometimes with grayish tinge (Sedifolia-gray pigment).Micarea flavoleprosa has a thick, wide-spreading yellowish green, whitish green to olive green sorediate thallus and lacks the Sedifolia-gray pigmentation. The species is mostly anamorphic, developing apothecia rarely. Micarea melanobola is characterized by a pale to dark vivid green granular thallus and darkly pigmented apothecia (Sedifolia-gray). Micarea pusilla is characterized by a whitish green to olive green thinly granular or membranous thallus, numerous and very small whitish apothecia lacking the Sedifolia-gray pigment, and by the production of methoxymicareic acid. Micarea fallax, M. flavoleprosa, and M. melanobola produce micareic acid. The reliability of crystalline granules as a character for species delimitation was investigated and was highly informative for linking the old type specimen of M. prasina to fresh material.