Description: This foliose lichen is rare, but easily recognised on account of its small, yellow-grey to greenish thallus (1-3cm diam.) and spots of yellow, powdery soredia on the lobes and lobe ends. It resembles a slightly smaller but more robust version of the rock-dwelling lichen Xanthoparmelia mougeotii (K+ orange medulla) attached to acid bark in the shape of a star. The species needs to be searched for more vigorously as it has only been recorded in Counties Antrim and Cork. It favours conifers such as larch and pine but will also grow on broadleaved trees in areas prone to bark acidification.

Key Identification Features:

• Small, yellow-green to greenish thallus spotted with yellow soredia (the same colour as Flavoparmelia caperata)
• On acid bark of conifers, worked timber and on broadleaved trees exposed to bark acidification; cortex is KC+ yellow, medulla K-.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Parmeliopsis ambigua at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Parmeliopsis ambigua at iNaturalist World Species Observations database.