Pseudevernia furfuracea chemotype inconsistencies

No answers, but I have also found several examples of Pseudevernia furfuracea with the same C- and KC pale pink (not red) reaction, and been confused by the texts. I thought from Dobson they were var. furfuracea, but cross-checking in LGBI2 and 3 made me doubtful (I don’t think I’d seen the Italic website then).

I’ve just re-tested two samples, several times, one from Warwickshire annd the other from Dolgellau, Wales. The C is definitely -ve (not fleetingly pink). (One sample had one odd spot that was pinkish before and after adding the C, but that was not typical.)

Also just looked at afl.lichenologie, which has var. furfuracea as KC-, C-, and var. ceratea as C+ (but no mention of KC).

I haven’t yet submitted any Pseudevernia records as I wasn’t sure which var. to call them (though my inclination is for var. furfuracea, as the C reaction is so decidedly negative). I’ve just noticed that I could use s. lat. though.

LGBI says var. ceratea is the commoner chemotype, albeit ‘particularly abundant in the north’.

Perhaps var. ceratea has a much stronger, redder reaction with KC? I haven’t yet found one with a C+ medulla.

Incidentally, there are no post 1960 records of P. furfuracea in Warwickshire, but I’ve found it in three different sites recently.

I can’t add much to the debate, other than questioning the evolutionary significance of the distinction between the two varieties. I have been accused of being allergic to varieties…

It seems that physodic and olivetoric acids (the two chemical culprits) are generated using the same gene cluster (see https://www.mdpi.com/2218-273X/11/10/1445” class=”bbcode_url”>https://www.mdpi.com/2218-273X/11/10/1445 if you are feeling brave) and so production can be influenced by regulatory and/or epigenetic factors rather than phylogenetic distinction.

Regarding recording, Pseudevernia furfuracea s. lat. (BLS 1192) can still be used, and indeed should be preferred in circumstances where there is doubt as to which of the varieties is present. You can add details of the chemical reactions to the notes field, which will guide others in the future when we have more data.

Best wishes

Paul

Thank you, Paul, for that link, which led down several rather deep but interesting rabbit holes. Apologies that this is probably not especially helpful. I agree that subspecies, varieties, etc often mean more time spent on details that tend to end up being inconclusive (with higher plants anyway), and/or not really useful. Nevertheless, I followed this up, as it was puzzling me.

One of the references in the link led indirectly to: “Pseudevernia furfuracea (L.)Zopf and its chemical races in the British Isles” by Hawksworth and Chapman in The Lichenologist, Vol 5, Issue 1-2 , October 1971, which gives the chemical reactions as stated in Dobson, that is, var. furfuracea being C- and KC rose-red. (It also refers to “the joint occurrence of these acids in a single specimen of this species” implying that most only had either physodic or olivetoric acid, which would mean that the KC rose-red was a reaction to physodic acid, rather than a faint olivetoric acid reaction.)

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In Orange’s ‘Microchemical Methods for the Identification of Lichens’ there is a reference to Hypogymnia physodes containing physodic acid. In LGBI it states that H. physodes also gives C- and KC red reactions (but it does also has other lichen acids). I tested a sample of H physodes, and it only gave a rather faint pink KC reaction.

An online search for “physodic acid KC” turned up a website about Hypogymnia species of North America:

“KC Test: Physodic acid is a very common substance in Hypogymnia that produces a KC+ orange, pinkish, or red color.”

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Wikipedia (admittedly not always a reliable source, but the bit about why it produces a colour was interesting) also says that physodic acid gives KC+ red. The linked reference (15) is Ahmadjian, Vernon; Hale, Mason E. (1973). The Lichens. New York: Academic Press.

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Could the references to var. furfuracea being KC- possibly be an error that has been copied across to other places?

About chemical spot tests.

The colored chemical reactions performed directly on lichens cannot alone characterize a lichen because they are not a complete chemical analysis (like a chromatography where the lichen compounds are separated before reacting with chemical agents to give a characteristic coloration) because they are performed on a mixture of chemical compounds and the coloration obtained is that of the mixture of the different colorations of each of the compounds taken individually. It is the chemical compound that has the highest concentration that contributes the most to the final coloration… so the interpretation can be difficult and the colorations obtained must be considered as a simple orientation.

On the other hand, current studies seem to show that the synthesis of the lichen compounds responsible for these colorations is not only the result of the action of the lichen genes, but that it also depends on the microbiome and environmental factors. So the colored reactions cannot alone characterize a lichen, it is just additional information (but sometimes very useful).

In the case of reaction C with sodium hypochlorite I have a few remarks to make:

_ The C solution used is generally made with bleach, which is not a pure chemistry laboratory solution but an industrial solution that contains NaOH (1-2%) and sodium chloride but also additives and dyes so it can give unexpected colors…

_ The pink or red coloring is very often fleeting and can go unnoticed. (It is often so fleeting that it is difficult to photograph). As for a C+ reaction, its interpretation is generally easy, we are indeed in the presence of the lichen substance sought (except in the rare cases where another substance has reacted in the same way!).

In the case of a C- reaction, the interpretation is more difficult and it is advisable to be careful because it is legitimate to ask questions:

_ Absence of the lichen substance sought?

_ Handling errors: corrupted C solution, temperature too cold or too hot, non-compliant pH, absence of ions necessary for the color reaction (Ca++, Mg++, etc.)…

That said, regarding Pseudevernie furfuracea, the KC reaction is often inapplicable in practice in the field because a possible pink or red coloration is masked by the very strong yellow coloration by K (and it is very difficult to differentiate a golden yellow from a pale orange (yellow + pink)! I think that we should “forget” this reaction in this specific case.

Furthermore, I think that making two varieties ceratea and furfuracea only on chemical characteristics that are difficult to highlight in the field as part of an inventory is excessive, two chemoforms would be sufficient, but it is not impossible that these two varieties exist, it would be very interesting to do more complete studies to properly pose the problem and to perhaps look for other characteristics that can be used in the field (In France ceratea is more frequent in the mountains).

Attached are some photographs to illustrate the discussion.

AG

PS. I noticed that in the case of the Pd reaction with var. ceratea it is Pd+ yellow, have you noticed the same phenomenon?