Calopadia cinereopruinosa

This lichen species forms a corticolous thallus that can be continuous or marginally dispersed into rounded, confluent patches. The thallus measures up to 30 mm (1+1⁄5 in) across and 20–40 μm thick, displaying a smooth, pale grey to greenish-grey colour. The apothecia are rounded, measuring 0.4–1 mm in diameter and 250–350 μm high, with a grey-black disc and a distinct white pruina. The apothecial margin is thick and prominent when young, also grey-black and white-pruinose.^[1]

The ascospores of Calopadia cinereopruinosa are single, oblong to ellipsoid in shape, muriform, and colourless, measuring 45–80 by 15–25 μm. The campylidia are sessile, with a well-developed, hood-shaped, grey lobe that is white-pruinose.^[1]

Calopadia cinereopruinosa closely resembles Calopadia subcoerulescens in terms of its grey-black apothecia and aeruginous hypothecium. However, the apothecia of Calopadia cinereopruinosa are thickly and persistently pruinose, a feature not observed in Calopadia subcoerulescens. The new species is also similar to Calopadia editiae, which forms pruinose apothecia and has ascospores shorter than 100 μm. However, Calopadia editiae has brownish apothecia with a yellowish tinge, and its hypothecium is light brown.^[1] Calopadia saxicola, a saxicolous (rock-dwelling) species growing on rocky seashores in southern Brazil, also has pruinose apothecia and muriform ascospores. However, C. saxicola has a corticate thallus with a brownish to reddish-brown apothecial disc and a brownish to dark brown hypothecium.^[2]

Calopadia cinereopruinosa is found in the Galápagos Islands, mainly on Isla San Cristóbal. It grows in the transition zone towards the humid upper parts of the island. Collections with campylidia have also been found on other islands, mostly in the humid zone. The species typically grows on bark of stems and twigs.^[1]