Molecular data resolve a new order of Arthoniomycetes sister to the primarily lichenized Arthoniales and composed of black yeasts, lichenicolous and rock-inhabiting species

Lichenicolous fungi belonging to the anamorph-typified genus Phaeosporobolus and to the teleomorph-typified genus Lichenostigma were isolated in pure culture or sequenced directly, with nuLSU and mtSSU sequences obtained. Phylogenetic analyses place the species of Phaeosporobolus in a strongly supported clade with the generic type of Lichenostigma (L. maureri), the genus Phaeococcomyces and several melanized rock-inhabiting isolates. This strongly supported nonlichenized lineage is sister to the primarily lichenized Arthoniales in the Arthoniomycetes and is here described as the Lichenostigmatales. The new order is characterized by cells multiplying by budding, either representing black yeasts, or species in which conidiomata and ascomata are entirely made of an organised agglomeration of spherical yeast-like cells. This way of life is not only very different from all other Arthoniomycetes that exist only in the mycelial stage, but ascomata and conidiomata representing a dense and organised agglomeration of yeast cells might be unique amongst fungi. A further difference with the Arthoniales is the absence of paraphysoids. Phylogenetic results suggest that Phaeosporobolus usneae is the asexual stage of Lichenostigma maureri. Most species of Phaeosporobolus are transferred to the genus Lichenostigma except P. trypethelii, for which the new genus Etayoa is described. The genus Diederimyces is reduced into synonymy with Lichenostigma. Several other members of Lichenostigma are placed in the Dothideomycetes and are intermixed with Lichenothelia species.