The Arthonialean challenge: Restructuring Arthoniaceae

Abstract

AbstractThe Arthoniales is the second–largest group of lichen–forming fungi. A new phylogeny of Arthoniales based on mtSSU, nLSU and RPB2 sequence data is presented, with a focus on crustose representatives. A total of 145 taxa are analyzed including 64 species of Arthoniaceae. We obtained 198 new sequences for 83 specimens representing 71 taxa of Arthoniales. Arthoniaceae is recovered as polyphyletic, demonstrating that previous classifications do not reflect evolutionary patterns. Three phylogenetic lineages are identified: the Arthoniaceae clade, the Bryostigma clade and the Felipes clade. The Bryostigma clade is related to Arthoniaceae, while the Felipes clade shows close affinities to Chrysotrichaceae. Cryptotheciaceae is included as a paraphyletic grouping in Arthoniaceae. Lecanographaceae and the genera Felipes and Melarthonis are described. Bryostigma and Pachnolepia are reinstated for former Arthonia species, and Myriostigma for the Cryptothecia candida complex. Fouragea is reinstated for foliicolous Opegrapha species. Arthonia eos is described and the new combination Alyxoria mougeotii is made. A lectotype is selected for Spiloma fallax. Melaspilea granitophila belongs in Arthoniaceae and Arthonia mediella in Chrysotrichaceae. According to the phylogenetic hypothesis, lichen secondary chemistry, such as pulvinic acid derivates or red pigments, does not characterize monophyletic groups above the genus level. The parasitic life style in Arthoniaceae has evolved more than once. Parasitic species are found in four lineages of the Arthoniaceae clade and in the Bryostigma clade. Arthoniomycetes with chlorococcoid photobionts are restricted to the Bryostigma clade and Chrysotrichaceae, while the only saprophytic Arthonia species in the phylogeny are related to Arthonia radiata and group with lichenized taxa. The phylogenetic data provide a coherent framework for delineating further monophyletic groups in Arthoniaceae in the future.