Observation 50018: Xanthoria elegans (Link) Th. Fr.
When: 2009-06-24
Herbarium specimen reported

Notes: on exposed sandstone in alpine

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Definitely a point we can all agree on
By: Jason Hollinger (jason)
2017-08-05 20:35:32 CDT (-0500)

lots of variation in widespread lichen species! (Indeed this variation may be the “trick” which enables these species to be successful over such a broad climatic and geographic range.)

I agree with Megan that the white coloration in the first photo is probably necrosis. I was a bit embarrassed that this photo was highlighted by wikipedia because I thought this looked like a “diseased” specimen! But I suppose there can be an aesthetic value even in death and struggle…

Lots of variation in lichens, to be sure, especially with cosmopolitan species across oceans
By: J-Dar
2017-08-05 17:43:00 CDT (-0500)

But nothing in these photos remotely resembles a lecideine apothecia.

Fair enough…
By: Megan (MeegsC)
2017-08-05 09:30:07 CDT (-0500)

I’m hardly an expert! :) And the whiteness may be dead material, of course. But those apothecia sure look lecideine in what I can see online. Of course, I also only know material from Europe, so it may be quite different there — I’m learning that many of these species vary wildly across the globe (and may indeed represent distinct species). I’m just trying to learn how to ID things, and this one looks very different from the rest of the examples on all of the X. elegans pages on MO…

You are welcome to your opinion…
By: Jason Hollinger (jason)
2017-08-04 16:52:26 CDT (-0500)

But I respectfully disagree. This looks right to me. Even the apothecia. :)

I suspect that what’s at issue here is there is a whole ocean of diverse morphotypes which all fit into the extremely broad concept of Xathoria elegans as presently used by lichenologists. All you need in (North America at least) to confirm X. elegans is a well-developed lower cortex throughout and no soredia(!)

I think the close-ups here clearly demonstrate that the lobes of this specimen are free of the substrate. They’re even imbricate — see the third and fourth photos, for example. Yes, not quite the same as seeing the lower cortex directly, but very suggestive.

As for thalline margin on the apothecia… Interesting. I haven’t ever paid attention to this character. (Remember, one only needs to demonstrate a lower cortex.) But since you mentioned it, I’m looking now… and it sure looks to me like they have entirely thalline margin and no proper margin (see fourth photo). I do look for a double margin in Caloplaca squamosa, and exclusively proper margin in the closely-related C. subsoluta. This looks like neither to me. This looks like entirely thalline. Admittedly this is a subtle character when the thallus and disk are the same color! But the texture and what little subtle difference in hue there is seem to confirm thalline margin. The left-most-center apothecium in the fourth photo shows this best, I think.

[EDIT: It is worth noting that the close-ups are of a different thallus than shown in the first photo. Fair enough. Even though taken from the same population, there could still be multiple species present. But I think all the characters mentioned above are still visible in the first photo. While most of the apothecia in the first photo are so old that they have lost their margin completely, there are still some young apothecia with an evident margin visible.]

Misidentified?
By: Megan (MeegsC)
2017-08-04 16:33:42 CDT (-0500)

Isn’t this a Caloplaca? X. elegans doesn’t show the white central section, and the apothecia are totally wrong; they should have a thalline border, which they don’t.

Featured picture on Wikipedia
By: Robert Sasata (Sasata)
2010-08-22 20:48:05 CDT (-0500)

Hi Jason, your first image of the elegant sunburst lichen shown here is now a “Featured Picture” on Wikipedia. See http://en.wikipedia.org/... for the voting. Thanks for contributing!

Created: 2010-08-09 00:30:17 CDT (-0500)
Last modified: 2017-08-05 17:42:00 CDT (-0500)
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