Observation 79758: Parmotrema reticulatum (Taylor) M. Choisy
When: 2011-10-16
Who: zaca
No herbarium specimen

Notes: This time I tried to use Spiman key to classify this specimen. As usual with keys, sometimes is not clear which alternative to take and the user as to make some options, often not correct.
Let me present some fact that we can give for this specimen which are documented in the attached photos:
- Thallus greenish grey (seems to me more green than gray);
- stained in some areas of a orangish-pinkish color that goes purple (I interpret this as the color coming from the medulla on desintegration);
- Sorediate at the lobe tips, some of lobe tips have pustules breaking into soredia;
- Very few cilia at the lobe tips, but some rhizines are visible in front view;
- Underside black covered with black short rhizines with a strip of brown around the margin of lobes;
- Chemical reactions: C- or C+ yellow very weak, K+ yellow to red, KC+ red.
Using the key mentioned above I made the following choices:
1 —> 51a —> 52b – 57a —> 58b (P. bangii).

Since I never heard about that species I thought about the possible existence in my country. Going to the portuguese checklist it does not appear there (which means almost nothing) but it appears in the checklist of the portuguese islands of Madeira and Azores. I also looked for images and I found one at lifedesks, where it is possible to see clearly the details of the thallus. The specimen shown there (I think it is an herbarium specimen since the color is off) was not stained but the details of the pustules and soredia are very similar to those my specimen.

Proposed Names

29% (1)
Used references: Spiman key, lifedesks.
Based on chemical features
56% (1)
Recognized by sight: fine cracking in upper surface; see comment

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
By: zaca
2011-10-18 13:25:45 CDT (-0400)

That was my first classification before I realize that maybe it was something else due to: 1) Almost complete lack of cilia, (2) Very subtle reticulate, (3) Existence of pustules.
Thanks, jason, for your opinion.

I would guess P. reticulatum
By: Jason Hollinger (jason)
2011-10-18 00:46:27 CDT (-0400)

A couple observations:

Presence of cilia is a really bad character to use, but unfortunately everyone does. I wouldn’t rule it out based on these photos. Actually, I rarely rule it out no matter how obviously lacking they seem to be. It always seems good practice to check both branches in the key just to be sure.

I think the most important character here is the fine network of faint cracks in the upper surface. (They are particularly visible on the lobes at the bottom of the first photo.) If I’m correct about that, then that puts it in the old Rimelia group. These are all listed on the ciliate branch (couplets 83 to 86), as it happens. Within that sub-branch, it keys readily to P. reticulatum, P. commensuratum or R. pontagrossensis. The last should just be South American(?) and should have a distinctly UV+y medulla. I don’t bother with the other two, since specimens with strong salazinic acid aren’t distinguishable without TLC. P. reticulatum is extremely common and widespread, so the odds at least are good.

I see what you mean about the soredia developing on pustules. But I would give more weight to the finely-cracked cortex. Oh, and I just found a specimen of P. reticulatum in my notes that looks exactly the same.

It’s more variable than the average Parmotrema. Some of my photos show abundant long cilia, others show none visible at all. The cracking is also variable, from extremely conspicuous to very subtle and invisible from a distance. (It should always be clear under a hand lens. But note that Sipman keys that one species out twice: once within Rimelia and again in choice 94a as merely “finely reticulately white-maculate”.)

Created: 2011-10-17 19:52:33 CDT (-0400)
Last modified: 2011-10-18 00:48:09 CDT (-0400)
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