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Images of British Lichens

Lecanora rupicola (L.) Zahlbr.
var. rupicola

Thallus crustose, chalky white to pale grey, smooth but extensively cracked-areolate, K+ yellow, usually lacking soralia (but blue soralia in var. efflorens); 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 and ultrabasic 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, 2013), 218-219 (photo); Wirth (1995), 1: 457 (photo), 483 (photo); Wirth et al. (2004), 213 (photo); Wirth, Hauck & Schulz (2013), 1: 582, 608 (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).

Lecanora rupicola
Lecanora rupicola, enlarged view
 On coastal rocks, St Martin's Haven, Pembrokeshire, May 2009. Arthonia varians is developing in some of the apothecia.
Lecanora rupicola
Lecanora rupicola
 On basic rock (basalt/trachyte) in old quarry, Luffness, East Lothain, September 2009.
Lecanora rupicola
 On coastal rocks, The Warren, South Devon, June 2010.
Lecanora rupicola, parasitised by Arthonia varians
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.
Lecanora rupicola, parasitised by Arthonia varians
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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© A.J. Silverside
Uploaded November 2008, substantially extended July 2010 & last updated February 2014