Graphidaceae

Graphidaceae is a family of lichen-forming fungi in the class Lecanoromycetes, order Graphidales. The family encompasses a diverse array of crustose lichens found worldwide, particularly in tropical and subtropical forests. It includes several well-known genera—Graphis, Ocellularia, Strigula, and Graphidea among others—and hundreds of described species. The name derives from Graphis, a prominent genus within the group.

Members are predominantly corticolous, growing on tree bark, though some occur on rocks or other substrates. They are characterized by crustose thalli and lirellate apothecia—long, narrow, slit-like fruiting bodies that often appear as black or dark lines across the thallus. The thallus is usually continuous and may be smooth, cracked, or areolate. Asci and ascospores vary by genus, with some species producing muriform (multi-segmented) spores; many species produce distinctive secondary metabolites.

Secondary chemistry is important in Graphidaceae; lichen substances such as lichexanthone and other xanthones are common and can be used in chemotaxonomy and UV fluorescence. Molecular phylogenetic studies have refined the circumscription of genera within Graphidaceae and clarified relationships to related families; ongoing revision continues to affect classifications.

Ecologically, Graphidaceae lichens contribute to nutrient cycling on bark and rock surfaces and serve as bioindicators of environmental conditions, including air quality and humidity. They are collected for biodiversity surveys and systematics, and their diverse chemistry provides taxonomic characters for species identification.