Xanthoriicola

Xanthoriicola is a fungal genus in the family Teratosphaeriaceae. It is a monospecific genus, containing the single species Xanthoriicola physciae, a lichenicolous (lichen-dwelling) fungus that grows exclusively on the fruiting bodies of the common orange lichen Xanthoria parietina. The fungus infects the reproductive structures (apothecia) of its host, turning them black, but displays an unusual non-destructive parasitic relationship where infected and healthy tissues coexist in close proximity for years without spreading. First described in 1865 and reclassified in 1973, it remained difficult to place taxonomically until molecular studies in 2011 revealed its relationship to extremophile fungi from Antarctica and parasites of human hair. X. physciae is widespread throughout Europe and notable for its unique ecological behaviour, with spores that disperse readily but rarely germinate under laboratory conditions.