Molecular phylogeny of the Pertusariaceae supports secondary chemistry as an important systematic character set in lichen-forming ascomycetes

Abstract

The Pertusariaceae is a diverse, cosmopolitan group of crustose lichen-forming fungi. It is particularly rich in secondary metabolites, containing a variety of compounds from different substance classes, such as xanthones, depsides, depsidones, and depsones. Morphology and chemistry-based studies have provided conflicting views of relationships among taxa, and phylogenetic relationships among genera in the Pertusariaceae are still unsettled. To evaluate these relationships, we generated a phylogeny based on nucleotide sequences of the nuclear large subunit (nu LSU) and the mitochondrial small subunit (mt SSU) rRNA genes. For a subset of taxa, we additionally sequenced the mitochondrial large subunit (mt LSU) rDNA. We studied a total of 49 taxa from the family Pertusariaceae and the enigmatic genus Loxosporopsis including four Agyrialean taxa used as outgroups. The alignments were analyzed using a Bayesian approach with Markov Chain Monte Carlo tree sampling (B/MCMC), and maximum parsimony methods. In the resulting phylogenetic estimates the genus Pertusaria in its current circumscription is polyphyletic comprising three major clades: the Pertusaria s.str.-group, the Variolaria-group and the Varicellaria-group. Loxosporopsis is closely related to Pertusaria s.str. We re-analyzed morphological, anatomical, and chemical features in the light of the molecular study and found novel character combinations to describe monophyletic entities. The taxonomic significance of particular secondary chemical constituents in the Pertusariaceae is corroborated.