Yes, it is known from the Channel Islands in southern California, as well “scattered localities in central and southern Europe”. It is narrow-lobed (< 0.5 mm wide), very closely attached to rock or bark, with “pustules dissolved into granulate soredia”, both cortex and medulla should have atranorin (K+ yellow).

I’d say this matches your specimen well. Another great observation! Probably the finest photos of this species on the web. :)

Yours matches the description on P. clementei in irishlichens.ie plausibly well, but not the photos. But here, look at these photos of allegedly the same species on a French site:

http://www2.ac-lille.fr/...

It shows “pustulate” soralia, much like yours. I’ll check for a description in my Sonoran Flora — we might have it in the southwest US as well, since there seems to be a fair overlap in flora between yours and that region.

… about the concrete species, althought the genus seems to be Physcia.
Your comment was appropriate, since it stated that my specimen has something between the granulated isiadia of P. clementei and piles of “capitate” soreda of P. caesia. Since, to the moment, I have no better proposal might be better to let it as Physcia sp..

P. caesia has piles of “capitate”, often blue, soredia; this specimen has pseudocorticate granular maybe even pustular soralia (it looks like the cortex is breaking up into granular fragments, instead of the medulla growing wild and forming piles of soft ecorticate granules). P. clementii might be worth considering, although the photos on irishlichens.ie show clear isidia, while yours shows something almost intermediate. Also note that P. caesia has broader lobes which are usually somewhat mottled, yours has minute, flat, evenly-colored lobes.