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This is such an old specimen, that the black underside – especially in the center – may not be significant. But in theory, if it is jet-black anywhere, then it should be P. borreri. I keep forgetting about it, because it is so rare in the US.
I would not conclude that P. jeckeri isn’t present just based on the absence from the “official” Portuguese checklist! :) Incidentally, supposedly at least, in Europe, among the other differences (presence of marginal soralia in addition to laminal round soralia, pruinose margins, and ~brownish cast(?) acc. to British Flora at least) P. jeckeri has shorter conidia (< 5 µm instead of > 5 µm). Might be hard to see without a high quality microscope, though.
Clearly the most common here is P. subrudecta. But this specimen, as other that I found in the past, has very weak C (+red) reaction, thus making me hesitate. On the other hand, In the British Flora, the black underside or pale brown to partly white divides the group of four Punctelia existing in UK in two groups: P. reddenda or P. borreri for the first group and P. subrudecta or P. jeckeri for the second group. I think P. jeckeri is ruled out because soralia is not mainly on ascending margins of the lobes. Since the underside I saw in the sample collected is black (this doesn’t mean that somewhere in the thallus it was not pale brown or brighter) I have no reason to decide between P. borreri and P. subrudecta. Because the chemical reactions where so weak, if I had to choose, then I would go towards P. borreri, but …
By the way, these two species, P. borreri and P. subrudecta, exhaust the portuguese checklist of Punctelia.
Created: 2012-09-10 16:29:12 CDT (-0400)
Last modified: 2012-09-10 16:29:14 CDT (-0400)
Viewed: 32 times, last viewed: 2015-09-27 16:53:02 CDT (-0400)