Observation 194391: Myelochroa aurulenta (Tuck.) Elix & Hale

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The yellow is very subtle sometimes.
By: Jason Hollinger (jason)
2015-05-07 16:32:40 PDT (-0700)

Ah well!

Jim Bennett just returned ID Myelochroa aurulenta
By: Andrew Khitsun (Andrew)
2015-05-07 16:27:49 PDT (-0700)

In his notes, he mentions that he found yellowish medulla.

Cryptic species…
By: Jason Hollinger (jason)
2014-12-22 22:12:22 PST (-0800)

… I think, is reserved for species which can’t be distinguished without molecular techniques. In this case we’re considering whether an unusual morphotype of M. aurulenta actually deserves taxonomic rank. It’s not ludicrous. New macrolichens are described, even here in North America, every year or so. Platismatia wheeleri was segregated out from P. glauca just a couple years ago. And it’s a remarkably obvious species once you know what to look for. There was a new Punctelia in Alabama recently, a new Sticta in North Carolina (may not even be published yet), new Hypogymnia and Bryoria are a dime a dozen in the Pacific Northwest. There was a new Parmelia up there a year or two ago, too. You get the idea! These were not cryptic species. Just talented observers noticing patterns either no one else had noticed, or had the time and/or resources to prove were “good” species.

What do they call it – cryptic species? (maybe I confuse my terms).
By: Andrew Khitsun (Andrew)
2014-12-22 17:23:29 PST (-0800)
Dust off your nobel acceptance speech again…
By: Jason Hollinger (jason)
2014-12-22 14:41:38 PST (-0800)

Must be an undescribed species! And maybe there really is something else hidden in Myelochroa aurulenta, because the degree of pigmentation in the medulla is certainly variable. As is the lobe width.

This genus has relatively complicated chemistry. Which is both a blessing and a curse. The problem is, if this specimen winds up having the same chemistry as M. aurulenta, it will be particularly difficult to justify calling a yellow-pigment-deficient, broad-lobed specimen a new species. :( But… if it has novel chemistry, then even a subtle difference like this can be considered strongly supported.

Problem is, your K+y medulla is entirely consistent, as far as it goes, with M. aurulenta, so you’d need TLC to get any farther.

So unfortunately, I think this will just end up being tossed on the vast M. aurulenta heap.

What the heck? (I usually say that when confused).
By: Andrew Khitsun (Andrew)
2014-12-22 13:03:23 PST (-0800)

I thought this was “just” Myelochroa aurulenta. However, I didn’t find any yellow medula under soredia (or elsewhere). The reason I took a photo and a specimen of this one was it looked too perfectly round for M.aurulenta. I applied K to the medula and received solid K+ yellow, both under soredia and in the middle of thallus. That also ruled out my other suspects – Flavoparmelia caperata and Canoparmelia texana. I used Thomson as a reference to analysis, but I am sure there are other ideas around. Lower surface black with lightening lobe tips (to very light tan in some places, but mostly brown). Rhizines appear to be simple, matted in the middle of thallus, growing all the way to the tip of the lobe.

Created: 2014-12-22 12:52:21 PST (-0800)
Last modified: 2015-05-07 16:26:51 PDT (-0700)
Viewed: 41 times, last viewed: 2017-09-25 13:03:21 PDT (-0700)
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