Phylogenetic placement of lichenicolous Phoma species in the Phaeosphaeriaceae (Pleosporales, Dothideomycetes)

More than twenty species of lichenicolous fungi have been described in Phoma , a large anamorphic genus of primarily plant-associated pathogens with broad geographic distributions. We obtained nuclear and mitochondrial rDNA sequences from 19 fungal cultures isolated from specimens representing four described and two undescribed lichenicolous species in the genus. Our multilocus phylogeny indicates that lichenicolous Phoma species represent at least two phylogenetically distinct clades in the Phaeosphaeriaceae, one including a new species, Phoma puncteliae, isolated from a specimen of Punctelia rudecta collected in Maryland, USA, and another group of primarily lichenicolous species. This latter group includes four described lichenicolous Phoma species, an unidentified melanized rock fungus, and a new lichenicolous Phoma species isolated from Xanthomendoza species collected in Canada that we are naming P. xanthomendozae. Some specimens in this clade collected from different lichen genera and species were found to be very similar genetically, which calls into question the recent practice of recognizing lichenicolous Phoma species mainly by differences in host preference.