Taxonomic Revision of Solorina (Peltigeraceae, Ascomycota), Reveals a New Genus and Three New Species

The lichen genus <i>Solorina</i> exhibits significant morphological and chemical variations between species. Recent molecular studies have demonstrated that <i>Solorina</i> is polyphyletic, underscoring the need for a comprehensive taxonomic revision. Phylogenetic analyses employing Bayesian methods and Maximum Likelihood approaches based on three molecular loci (nrITS, nrLSU, mtSSU) revealed that species of <i>Solorina</i> segregate into two distinct clades. The first clade includes species characterized by bright orange lower surfaces that contain secondary metabolites, notably solorinic acid. The type species, <i>Solorina crocea</i>, is retained in the genus <i>Solorina</i>. The second clade encompasses species with white or brownish lower surfaces; most species lack secondary metabolites and are now classified as a new genus, <i>Pseudosolorina</i>. As a result of this taxonomic revision, two species: <i>S. crocea</i> and <i>S. crocoides</i> remain in the genus <i>Solorina</i>. Five species with white or brownish lower surfaces were transferred to the new genus <i>Pseudosolorina</i>, which consists of three newly described species and five new combinations. Four species previously described as <i>Solorina: S. embolina</i>, <i>S. fuegiensis</i>, <i>S. octospora</i>, and <i>S. platycarpa</i> have morphology consistent with <i>Pseudosolorina</i>, but are currently retained in <i>Solorina</i> due to the absence of supporting DNA sequence data. A key to <i>Solorina</i> and <i>Pseudosolorina</i> is provided. The spores of <i>S. crocea</i> exhibit wall ornamentation featuring rounded papillae, which are distinct from those of <i>Pseudosolorina</i>. Molecular data and morphological characters also indicate that both <i>Solorina</i> and <i>Pseudosolorina</i> engage in symbiotic associations with photobionts cyanobacteria <i>Nostoc</i> and chlorophytes <i>Coccomyxa</i> or <i>Asterochloris</i>.