Four new species of the lichen genus Diorygma (Graphidaceae, Ostropales) from Guizhou, China

Four new species of the lichen genus <i>Diorygma</i> from China are described based on morphological, chemical, and phylogenetic evidence. Phylogenetic analyses were conducted using both RAxML and Bayesian posterior probability inference, based on combined LSU and mtSSU sequences. The characteristic compounds were analyzed by colorimetric reactions and thin-layer chromatography. <i>Diorygma guizhouense</i> is characterized by small apothecia, a narrow to slightly open disc covered with white pruina, and the presence of stictic, salazinic, and norstictic acids. <i>Diorygma leigongshanense</i> is characterized by small, oval apothecia, a disc surrounded by entire, raised, and widely open thalline margins covered with thin, pale yellowish pruina, and the same chemical substances as <i>D. guizhouense</i>. <i>Diorygma locitonitrus</i> is distinguished by the presence of salazinic acid and hyaline, richly muriform ascospores, notably with distinctly smaller peripheral cells compared to the central cells. <i>Diorygma weii</i> is characterized by stellately branched apothecia with a closed to slit-like disc, a milky white thallus tinged with green, and the presence of only norstictic acid. Detailed morphological descriptions and illustrations of the new species are provided, along with a comprehensive species checklist highlighting the diagnostic characteristics of the known species in this genus.