Parmeliopsis hyperopta (images of British lichens)

Very similar to P. ambigua (of which it may well be no more than a chemical variant lacking usnic acid), differing in the grey to blue-grey thallus, with soredia white to pale, blue-grey. As in the case of P. ambigua, primarily a species of acid bark, especially conifer wood, in central and eastern Scotland, often with P. ambigua, but rarer, very scarce elsewhere, showing much more limited spread as a result of sulphur dioxide pollution, and disappearing again as SO₂ levels have dropped. Very easily confused with Imshaugia aleurites, differing in being sorediate with intitially well delimited, convex soralia, whereas I. aleurites is isidiate, with isidia formed individually from the thallus surface

Refs: Smith et al. (2009), 660; Purvis et al. (1992), 250 (as Foraminella hyperopta); Jahns (1983), 204-5 (photo); Dobson (2005), 309 (excluding photo which can be seen to be isidiate and is Imshaugia); Dobson (2011), 310 (again excluding photo); Hansen & Anderson (1995), 48 (photo); Wirth (1995), 2: 671-672 (photo); Moberg & Holmåson (1984), 98 (photo); Nordic Lichen Flora (2011) 4: 94, 164 (photo); Hinds & Hinds (2007), 346 (photo); Pope (2005), 35 (photo); Brodo et al. (2001), 489, 490 (photo); McCune & Geiser (2009), 229 (photo).

Some authors give additional characters to separate P. hyperopta and P. ambigua (see, e.g., Hinds & Hinds, 2007), but these seem not to be applicable over wider areas and it may well be that there are a number of minor geographical variants, some with usnic acid and some without. While DNA work (Lichenologist 33: 403-8, 2001) seems to support separation of "P. hyperopta" and "P. ambigua", this is work on an asexually reproducing species in just one limited area; it remains to be shown that grey and yellow-green variants represent distinct single lineages within the overall range of the species-complex.

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Images of British Lichens