Notes on lichenicolous species ofOpegraphas. lat. (Arthoniales) onArthoniaceaeandVerrucariaceae, with a key to British and Irish lichenicolousOpegraphaceae

Abstract

AbstractThree species of lichenicolousOpegraphas. lat. are newly described, all apparently host-specific at genus level.Opegrapha arthoniicolaCoppins & S. Y. Kondr. is described from western Britain and Ireland, where it grows on the thallus ofArthonia radiataonCorylusbark; it has small clustered ascomata, asci that are usually 6-spored and rather small ascospores (10.5–)12.5–14.5 μm in length.Opegrapha sawyerianaCoppins occurs on the thallus ofConiocarpon cinnabarinum, also onCorylusbark, from oceanic western parts of Scotland, Ireland and southern England; in comparison toO. arthoniicolait has smaller, often scattered ascomata with a pigmented basal layer, 8-spored asci and slightly larger ascospores 13–14.5(–16) μm in length.Opegrapha hochstetteriCoppins has been found on thalli ofVerrucaria hochstetteriandV. muralison calcareous rocks and stonework in southern England and Luxembourg; collections were formerly identified asOpegrapha rupestrisPers. but it differs from this species by narrower ascomata with a persistent narrow slit, normally 6- rather than 8-spored asci and ascospores with pigmentation in the spore wall rather than the perispore. Lifted from synonymy isOpegrapha opacaNyl., which inhabits the thallus ofVerrucaria nigrescensandV. viridulaon calcareous rocks and stonework, and is so far recorded from southern England, Luxembourg, France, northern Spain and Israel. The hosts of the European species of lichenicolousOpegraphaonVerrucarias. lat. on calcareous rocks (O. hochstetteri,O. opacaandO. rupestris) belong to different phylogenetic lineages within theVerrucariaceae. A key is also provided to the lichenicolous species ofOpegraphaceaecurrently known from Great Britain and Ireland.