The taxonomy of the genus Graphis sensu Staiger (Ascomycota: Ostropales: Graphidaceae)

Abstract

AbstractThe species-level taxonomy of the genus Graphis sensu Staiger was revised using numerical taxonomy and cladistic techniques. In its current circumscription, Graphis includes more than 300 species and is characterized by lirellae with well-developed, carbonized labia usually concealing the disc and usually hyaline, I+ blue-violet, transversely septate to muriform ascospores. The study analyzed the importance of morphological, anatomical, and chemical characters for taxonomic purposes in the genus, both at species level and at the level of species groups and lineages. A phenotype-based cladistic analysis, combined with a novel method to estimate the degree of character state homoplasies prior to a cladogram, as well as a species ordination using non-metric multidimensional scaling (NMS), was performed to assess the delimitation of potentially natural groups within the genus. Contrary to previous views, the most important character complex characterizing potentially natural groups in the genus Graphis is lirellae morphology, whereas labia striation, excipulum carbonization, ascospore features, and secondary chemistry, vary greatly even in closely related species. Based on these findings, Wirth and Hale's concept of ‘sporomorphs’ is emended to generally characterize morphologically similar species that differ in a single character, such as labia striation (‘labiomorph’), excipulum carbonization (‘excipulomorph’), hymenium inspersion (‘inspersomorph’), ascospore size and septation (‘sporomorph’) and secondary chemistry (‘chemomorph’).