Two new species of Rhizoplaca (Lecanoraceae) from Southwest China

In this study, two new species, Rhizoplaca adpressa Y. Y. Zhang & Li S. Wang and R. auriculata Y. Y. Zhang, Li S. Wang & Printzen, are described from Southwest China, based on their morphology, phylogeny and chemistry. In phylogeny, the two new species are monophyletic, and sister to each other within Rhizoplaca chrysoleuca-complex. Rhizoplaca adpressa is characterized by its placodioid and closely adnate thallus, pale green and heavily pruinose upper surface, narrow (ca. 1 mm) and white free margin on the lower surface of marginal squamules, the absence of a lower cortex, and its basally non-constricted apothecia with orange discs that turn reddish-brown at maturity. Rhizoplaca auriculata is characterized by its squamulose to placodioid thallus, yellowish green and marginally pruinose squamules, wide (1−3 mm) and bluish-black free margin on the lower surface of marginal squamules, the absence of a lower cortex, and its basally constricted apothecia with persistently orange discs. Rhizoplaca adpressa and R. auriculata share the same secondary metabolites of usnic and placodiolic acids.