Muellerella, a lichenicolous fungal genus recovered as polyphyletic within Chaetothyriomycetidae (Eurotiomycetes, Ascomycota)

Molecular data and culture-dependent methods have helped to uncover the phylogenetic relationships of numerous species of lichenicolous fungi, a specialized group of taxa that inhabit lichens and have developed diverse degrees of specificity and parasitic behaviors. The majority of lichenicolous fungal taxa are known in either their anamorphic or teleomorphic states, although their anamorph-teleomorph relationships have been resolved in only a few cases. The pycnidium-forming Lichenodiplis lecanorae and the perithecioid taxa Muellerella atricola and M. lichenicola were recently recovered as monophyletic in Chaetothyriales (Eurotiomycetes). Both genera are lichenicolous on multiple lichen hosts, upon which they show a subtle morphological diversity reflected in the description of 14 species in Muellerella (of which 12 are lichenicolous) and 12 in Lichenodiplis. Here we focus on the teleomorphic genus Muellerella and investigate its monophyly by expanding the taxon sampling to other species occurring on diverse lichen hosts. We generated molecular data for two nuclear and one mitochondrial loci (28S, 18S and 16S) from environmental samples. The present multilocus phylogeny confirms the monophyletic lineage of the teleomorphic M. atricola and M. lichenicola with their L. lecanorae-like anamorphs, but places the rest of the Muellerella species studied in two different monophyletic lineages with strong support. The first, Muellerella spp. 1, is nested within some new lineages of black fungi isolated from different epilithic lichen thalli, while the second, Muellerella spp. 2, is closely related to the Verrucariales. Based on these results, we reappraise the phylogenetic placement of Muellerella and suggest its polyphyly within Chaetothyriomycetidae.