Description: This species and the recently described C. oasis are easily confused as both species have an overlapping parasitic and non-parasitic lifestyle. In Ireland, C. polycarpa has most often been recorded as a parasite of Verrucaria spp., commonly V. baldensis which it can cover in orange, circular patches. C. oasis differs in its yellow, never orange, less areolate thallus and thinner disc margins. It is most abundant in areas of naturally occurring limestone. In Ireland, three clusters of recent records, for example, Counties Kerry and Clare.

Key Identification Features:

• Parasitic on Verrucaria spp., on natural limestone outcrops and old castle walls
• Forms small circular orange or orange-yellow patches; becoming areolate; discs common.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Caloplaca polycarpa at iNaturalist World Species Observations database.