Lecanora variolascens?

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Neil Sanderson
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Lecanora variolascens?

Post by Neil Sanderson » Thu Apr 01, 2021 10:27 pm

I collected a rather odd looking Lecanora from an Oak branch leaning out over a glade in the New Forest the weekend before last. It was sorediate, strongly K + yellow (so not Lecanora jamesii) and fertile, it looked quite like Lecanora barkmaniana but the disks were strongly pruinose, which did not seem right, and the colour was paler than usual. I nearly left it, but collected it.

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Scan of specimen, Thalline margin with Pd + yellow reaction on far left centre

The thallus is greyish-white and verrucose, with white low mounds of delimited white soralia and is K + yellow, Pd+/– faint yellow, while there is a stronger reaction Pd + yellow reaction on the thalline margin. The thalline margin has large crystals but I did not find any spores. I will have a go again tomorrow.

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Closer scan of thallus

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Apothecia with pruina under microscope

There is a useful paper in the Lichenologist on European sorediate Lecanora s. lat. Malíček et al (2017) "Corticolous sorediate Lecanora species (Lecanoraceae, Ascomycota) containing atranorin in Europe" https://doi.org/10.1017/S002428291700038X or https://www.researchgate.net/publicatio ... _in_Europe. In this the lichen keys out as Lecanora variolascens. This is closely related to Lecanora barkmaniana and differs in the strongly pruinose disk and smaller spores in Lecanora variolascens. The pictures of Lecanora variolascens look very like mine. There are also accounts at https://www.afl-lichenologie.fr/Photos_ ... ascens.htm and http://italic.units.it/index.php?proced ... e&num=1271

Malíček et al (2017) give the habitat as
Occurs on ±acidic bark (mainly of oaks and pines) but usually in slightly eutrophicated places
Which also matches the Oak branch it was on. It appears to be rare and very infrequently recorded. Looks promising, I will just see if I can find spores tomorrow.

Niel
Last edited by Neil Sanderson on Fri Apr 02, 2021 7:51 pm, edited 3 times in total.
Neil Sanderson

maxieput901
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Re: Lecanora variolascens?

Post by maxieput901 » Fri Apr 02, 2021 9:44 am

This is exciting, Neil. Will the honeypot of the New Forest keep yielding up its secrets? Good luck with finding a spore or two.

Neil Sanderson
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Re: Lecanora variolascens?

Post by Neil Sanderson » Fri Apr 02, 2021 11:26 am

I had another go today wiht the candidate Lecanora variolascens. Spent some time looking for spores and looking at the internals of the apothecia, finally finally found a couple spores:

Thaline margin with large crystals, not soluble in K. Epihymenium reddish brown, paler in K, course brown granules on the surface, soluble in K. Asci mainly sterile 25 – 30 x 15 – 19µm, spores rare, a couple found 8 x 5µm.

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Apothecia cross section, I polarised light below

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Slight squash in water

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Harder squash in water, showing the K soluble brown crystals in the Epihymenium

This, encouragingly, mostly matches Lecanora variolascens. The few spores I found were at at, or just below, the bottom end of the ranges given by the three sources (8-12.5 x 5-9 μm in Italic 6 to (9·0–) 10·0–12·5 × 6–8(–9) in Malíček 2017), but given the only other alternative, Lecanora barkmaniana, has bigger spores (12–15 × 8·5–10·0μm in Malíček 2017) than Lecanora variolascens, this seems OK. I will get a second opinion and see.

The information in Malíček et al (2017), suggest the species has been overlooked (most specimens they identified were miss-named herbarium specimens), but that it is also scattered and rare.

Neil
Neil Sanderson

Neil Sanderson
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Re: Lecanora variolascens?

Post by Neil Sanderson » Thu Apr 08, 2021 2:10 pm

I sent the pictures to Jiří Malíček, who agrees with the determination; so a nice new Lecanora for Britain. It seems, like the closely related Lecanora barkmaniana, it is often sterile, when it will be difficult to spot, basically a whiter version of Lecanora barkmaniana, in more acid and less enriched habitats. Fertile it it easy to do, with the combination of pale soralia, strongly pruinose disks and smaller spores.

Neil
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