Observation 102306: Evernia mesomorpha Nyl.

When: 2012-07-20

Collection location: Hunlock Creek, Pennsylvania, USA [Click for map]

Who: Dave W (Dave W)

Specimen available

Growing on a metal rural mailbox. Specimen is soft/flexible, white cottony inside. Looks like E. prunastri… however, Brodo lists shows no record of this species in PA, and lists it as “extinct” in Ontario.

Proposed Names

29% (1)
Recognized by sight
Used references: Brodo
84% (1)
Recognized by sight

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Glad to help
By: Jason Hollinger (jason)
2012-07-23 07:06:44 CEST (+0200)

(and I hope the analysis was right! :)

Thanks so much for the detailed analysis, Jason.
By: Dave W (Dave W)
2012-07-23 05:32:10 CEST (+0200)

My wife Karen is interested in lichen. Looks like she’s got some homework :-) Like I said previously, this is a great way to learn technical stuff a little bit at a time, within the context of one’s own observations.

Fair enough
By: Jason Hollinger (jason)
2012-07-21 23:40:02 CEST (+0200)

The lighter underside is not so visible in the photos, but I take your word for it. These things are hard to characterize perfectly. There are always specimens like this which challenge the definition of typical material for the species.

So let’s go more technical. Other differences between the two species:

One has evernic acid, the other divaricatic acid. Too bad, both are K- C- KC- and UV+ white, so no help unless you have access to TLC!

E. prunastri has atranorin in addition to usnic acid in the cortex, E. mesomorpha just has usnic acid. This manifests visually as E. prunastri typically being grayer than your specimen. It is technically K+ faint yellow, but in practice, especially in a particularly green specimen like this, it’s not easy to be confident that it completely lacks atranorin. And because KOH (or water in general) makes the cortex transparent, there’s a tendency for K test on usnic species to look sort of ambiguously K+ weak yellow as it reveals the slightly yellowish green of the algal layer. I don’t like to trust this test myself.

Another difference: E. prunastri has strictly sorediate soralia which at least start out clearly delimited into discrete soralia mostly along the margin (but also appearing in the center of branches). E. mesomorpha has “subisidioid” soredia scattered all over and never confined to discrete soralia. Yours (the last photo) clearly shows scattered granular isidioid soredia, and I can find no examples that I’d call “clearly delimited soralia”.


1) many (if not all) branches are “angular”
2) not “grayish” suggesting lack of atranorin
3) isidioid, scattered soredia

I still feel confident calling this E. prunastri despite the ambiguity of this particular specimen, and despite how exciting it would be for you to report the first record of E. mesomorpha in Pennsylvania on Mushroom Observer!

Thanks for all the info, Jason.
By: Dave W (Dave W)
2012-07-21 23:18:54 CEST (+0200)

Though the branches aren’t as flat and straplike as shown in Brodo’s photo of E. prunastri, they are definitely white on the lower halves of one side. You can see a bit of that in the 2nd photo. The branches are quite twisted and have rolled edges. You may be right that it’s mesomorpha though.

Looks more like Evernia mesomorpha
By: Jason Hollinger (jason)
2012-07-21 19:58:34 CEST (+0200)

There’s a photo in The Macrolichens of New England that looks exactly like yours. E. prunastri has much more obviously flattened branches, and which are typically lighter on one side than the other. As a matter of interest, New England flora cites a number of specimens of E. prunastri in New England area:

north Great Lakes – Hale 1979
Newfoundland – Ahti 1983b
Novascotia – Casselman & Hill 1995
Willmington, MA – 1999, D. Greene
coastal Maine – 1904, G.K. Merrill

Additional sources:

Ontario, New Brunswick, P.E. Island – “GS” macrolichen status for Canada
New Brunswick – 2011 Tuckerman workshop
Ontario – Wong & Brodo 1990
Michigan – several sources
Wisconsin – J. Bennett

So it’s exceedingly rare, even north of you. (But extremely common in the Pacific Northwest.)

Created: 2012-07-21 16:22:06 CEST (+0200)
Last modified: 2012-07-21 23:40:23 CEST (+0200)
Viewed: 71 times, last viewed: 2017-06-13 15:40:15 CEST (+0200)
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