Lecanora rupicola (images of British lichens)

Lecanora rupicola (L.) Zahlbr.

Thallus crustose, chalky white to pale grey, smooth but extensively cracked-areolate, K+ yellow, usually lacking soredia; apothecia initially innate, pinkish buff but covered by a thick, white to grey pruina, testing yellow with sodium hypochlorite (bleach), becoming strongly convex when mature and healthy. Widespread, but rare in the south-east, on siliceous rocks, pebbles and walls.

Refs: Smith et al. (2009), 495; Purvis et al. (1992), 313; Dobson (2005), 230 (photo); Dobson (2011), 233 (photo); van Herk & Aptroot (2004), 218-219 (photo); Wirth (1995), 1: 457 (photo), 483 (photo); Wirth et al. (2004), 213 (photo); Moberg & Holmåson (1984), 115 (photo); Puntillo (1996), plate 22 (photo); Brodo et al. (2001), 387 (photo); Thomson (1997), 302-3 (photo).

Very commonly parasitised by Arthonia varians, which blackens the apothecia and arrests their development (examples below).



	On coastal rocks, St Martin's Haven, Pembrokeshire, May 2009. Arthonia varians is developing in some of the apothecia.


	On basic rock (basalt/trachyte) in old quarry, Luffness, East Lothain, September 2009.

	On coastal rocks, The Warren, South Devon, June 2010.

	On stonework of old bridge, Kindrogan, Perthshire, March 2008. The blackened, immersed apothecia and also, I think, the more mature, pruinose apothecia at the bottom right, are parasitised by Arthonia varians, resulting in a lichen with a superficial resemblence to Lecidea grisella, with which it was growing. Perhaps only one apothecium (near top right, arrowed) is developing normally. The photograph shows the positive, yellow, bleach test result on the apothecia, reaction somewhat smeared over the adjacent thallus.

	On coastal rocks, St Martin's Haven, Pembrokeshire, May 2009, parasitised by Arthonia varians. Here the apothecia of L. rupicola are less pruinose, and so more starkly black as a result of the parasitism. There is potential for confusion with the black apothecia of Aspicilia cinerea and its allies.

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Images of British Lichens