Observation 196071: Acarospora A. Massal.

On sandstone boulder in full sun, occurring on the shady side of the rock.


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Great tip!
By: J-Dar
2015-02-01 10:22:31 CST (-0600)

Thanks, I hope to get down to this location soon and will definitely run a test as suggested.

Great tip!
By: J-Dar
2015-02-01 10:20:18 CST (-0600)

Thanks, I hope to get down to this location soon and will definitely run a test as suggested.

Quick gentle warning…
By: Jason Hollinger (jason)
2015-01-19 22:30:34 CST (-0600)

The C test for gyrophoric acid (what we’re testing for here) is notoriously fleeting and subtle. The ideal method is to test it under a dissecting scope, of course, but in the field you may still have luck if you scratch it a bit then apply your C with a toothpick or something more controlled than an eye-dropper. A big drop will bleach away any positive reaction so quickly you may never see it. Another option is to apply K first then C. The KC reaction is a bit stronger and more persistent. Zaca manages frequently to get photos of positive KC tests in the field (god alone knows how!)

By: Jason Hollinger (jason)
2015-01-19 10:51:42 CST (-0600)

And maybe even this time… I’d give it 50-50 odds that these two thalli are the same species. :) You just chose a hard one to start with.

Is there ever just one??
By: J-Dar
2015-01-19 10:39:11 CST (-0600)

Let’s make this observation about the main specimen highlighted in the first photo. I’ll get back to this rock some day with some C and keys, maybe we can figure it out.

I wonder if there might be two species here…
By: Jason Hollinger (jason)
2015-01-11 23:33:59 CST (-0600)

The texture, color, density and size of the areoles of the thallus in the bottom left all look subtly different from the main thallus in the center.

Options include (based on Sonoran Flora key and CNALH maps):

A. robiniae – C+r
A. socialis – C-, areoles scattered
A. contigua – C-, areoles contiguous

A. socialis is very common in southern CA. And maddeningly variable. A. contigua has been misused in the past, so the maps might not be trustworthy, it might not occur in southern CA. A. robiniae… well, who can say without a C test? :( Here’s what Knudsen says in the notes for A. robiniae in the Sonoran Flora:

Besides the occurrence of gyrophoric acid [C+r] in the cortex, A. robiniae differs from A. socialis in having a broad attachment of its areoles, a brighter yellow color, yellow discs…

In A. socialis, by contrast, the areoles become raised from the substrate, eventually becoming stipitate and subsquamulose, and the apothecial discs are usually brown to reddish-brown.

Perhaps the larger central thallus is A. robiniae and the smaller paler one on the bottom left is A. socialis? Alas, there really is no way to be confident without seeing a specimen in hand. :(