A new circumscription of the genus Varicellaria (Pertusariales, Ascomycota)

The lichen-forming genus Pertusaria under its current circumscription is polyphyletic and its phylogenetic affiliations are uncertain. Here we study the species of the genera Pertusaria and Varicellaria which contain lecanoric acid as major constituent, have disciform apothecia, strongly amyloid asci, non-amyloid hymenial gel, 1-2-spored asci, and 1- or 2-celled ascospores with thick, 1-layered walls. We infer phylogenetic relationships using maximum likelihood and Bayesian analyses based on four molecular loci (mtSSU, nuLSU rDNA, and the protein-coding, nuclear RPB1 and MCM7 genes). Our results show that the lecanoric acid-containing species form a well-supported, monophyletic group, which is only distantly related to Pertusaria s.str. The phylogenetic position of this clade is unclear, but placement in Pertusaria s.str. is rejected using alternative hypothesis testing. The circumscription of the genus Varicellaria is enlarged to also include species with non-septate ascospores. Seven species are accepted in the genus: Varicellaria culbersonii (Vězda) Schmitt & Lumbsch, comb. nov., V. hemisphaerica (Flörke) Schmitt & Lumbsch, comb. nov., V. kasandjeffii (Szatala) Schmitt & Lumbsch, comb. nov., V. lactea (L.) Schmitt & Lumbsch, comb. nov., V. philippina (Vain.) Schmitt & Lumbsch, comb. nov., V. rhodocarpa (Körb.) Th. Fr., and V. velata (Turner) Schmitt & Lumbsch, comb. nov. A key to the species of Varicellaria is provided.