The ascomycete genus Xylographa includes some of the most abundant species of wood-inhabiting lichenized fungi in boreal and temperate regions. It has never been monographed and little is known of its species diversity and evolutionary relationships. Based on a morphological and secondary metabolite-based assessment of material from North and South America, Europe and Asia, we generated a three-locus phylogeny based on sequences of the internal transcribed spacer, 28S nuclear rDNA and mitochondrial small subunit rDNA. We analyzed the data within the context of putatively related genera in the order Baeomycetales. Xylographa is a strongly supported monophyletic group closely related to Lithographa and Ptychographa, as well as rock-dwelling and lichenicolous species of Rimularia s.lat. The evolution of linearized ascomata in Xylographa appears to have enabled ascomata to grow laterally, and patterns of lateral growth are diagnostic. We recognize twenty species in Xylographa and provide a thorough revision of nomenclature. The following eight species are new: Xylographa bjoerkii T. Sprib., X. constricta T. Sprib., X. erratica T. Sprib., X. lagoi T. Sprib. & Pérez-Ortega, X. schofieldii T. Sprib., X. septentrionalis T. Sprib., X. stenospora T. Sprib. & Resl and X. vermicularis T. Sprib. The combinations Lambiella insularis (Nyl.) T. Sprib. and Xylographa carneopallida (Räsänen) T. Sprib. are newly proposed. Xylographa constricta from southern South America represents the first known case of secondary de-lichenization in the Baeomycetales. Xylographa parallela s.str. is confirmed as bipolar on the basis of sequenced collections from both southern Chile and the northern Hemisphere.
Keywords: Ascomycota; Fungi; biodiversity; evolution; lignicolous; phylogenetics; saproxylic; taxonomy.