Candelaria pacifica
Candelaria pacifica has been recently identified from Britain. It is similar to the well known Candelaria concolor, but this has larger, more distinctly lobate squamules with neat branching and usually forms distinct rosettes. In contrast, C pacifica is minutely squamulose, frequently coalescing into a mass of congested squamules. The most diagnostic feature is that the lobes of C. pacifica lack a lower cortex, producing an eroded and greenish underside. The undersides of the lobes of C. concolor have a distinct cortex, so are white and shiny. Grows in similar nutrient enriched habitats as C. concolor but appears rarer.
See Fungi of Great Britain and Ireland for more pictures. There are also high quality images by Norbert J. Stapper at link, comparing both species.
Thallus small, very variable, of scattered, minute squamules or minutely foliose or subfruticose, rarely forming weakly defined rosettes to 5 mm diam., usually coalescing to form extensive colonies. Lobes mostly raised to erect, branched, to 0.5 (–2) mm long and 0.1–0.3 mm broad, shade forms typically consisting of erect, very narrow lobes, lemon yellow (in shade) to bright yellow, smooth to somewhat pulverulent, with copious blastidia 30–100 μm diam. formed primarily from the lobe margins, sometimes almost completely dissolved into blastidia with few visible lobes; thallus corticate above, cortex very uneven, lower surface irregular and ecorticate, arachnoid, white to greenish; rhizines rarely present, minute. Apothecia and conidiomata not known in European material. Thallus C–, K–, KC–, Pd–, UV± dull orange.
Similar to Candelaria concolor but with more delicate and copiously blastidiate thallus lobes, which are often coalesced into crusts. Colonies which are densely blastidiate with inconspicuous lobes could be overlooked as welldeveloped thalli of Candelariella xanthostigmoides (Candelariella reflexa).
On nutrient-enriched bark of broad-leaved trees, sometimes also on worked timber.
Probably still very under recorded, S.E. England, Shropshire, E. Scotland
Cannon, P., Coppins, B., Orange, A., Sanderson, N. & Simkin, J. (2021). Candelariales: Candelariaceae, including the genera Candelaria and Candelariella. Revisions of British and Irish Lichens 21: 1-8. Link.
Stapper, N. J. (2012) Bestimmungshilfe zur Unterscheidung von Candelaria concolor und C. pacifica 1. Illustrierte Bestimmungshilfe zur Unterscheidung von Candelaria concolor und Candelaria pacifica. Archive for Lichenology. 7 Link.
Text by Neil A Sanderson based on Cannon et al (2021)