Chaenotheca: a Pd/UV Reaction & a Question

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Neil Sanderson
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Chaenotheca: a Pd/UV Reaction & a Question

Post by Neil Sanderson » Thu Mar 21, 2019 9:39 am

I have another positive UV/Pd test, one that Mark was interested in, and a query on a Chaenotheca specimen.

The positive UV/Pd test, was from Chaenotheca stemonea, collected from a leaning ancient Oak in Mallard Wood, New Forest. This species is supposed have a Pd + yellow thallus but the strength of the reaction is very variable and often week. Occasionally I have made it out in the field but more often this is not possible, although usually a yellowing of the thallus with Pd can be just made out under a binocular microscope. The Mallard Wood specimen is a classic, quite easily identified in the field by the thin loose farinose pale yellowy green thallus and stalked apothecia with black stalks with white pruina under the very round head. The Pd reaction was just visible under a binocular microscope, but the spot test was brightly yellow fluorescent under UV. The LGBI2 gives Chaenotheca stemonea a having barbatic and obtusatic acids, I assume the reaction is due to the second acid?

My question concerns a similar looking sterile thallus from northern England, found when following up some old records of Chaenotheca gracilenta from Elm trees for Plantlife, looking at a couple of Yorkshire sites: Fountains Abbey (SE2769) and Kilton Beck, Loftus (NZ7017). At the former the Elms were gone and there seemed little chance of survival, but I did find lots of good pinheads, including Chaenotheca stemonea, new to Northern England. At Loftus, however, the remarkable ravine woodland here still had live old Wych Elms and a surprisingly rich lichen assemblage in spite of the proximity of Teesside and its industry. These included Ramonia chrysophaea and Agonimia flabelliformis new to NE England and a large population of Inoderma subabietinum.

Here I found a sterile thallus on an old Wych Elm, with a bright green loose leprose thallus, Stichococcus algea which was UV –, Pd – and Pd/UV –. The leprose thallus with Stichococcus suggests Chaenotheca furfuracea, Chaenotheca stemonea or Chaenotheca gracilenta.

Chaenotheca furfuracea: should be UV± lemon-yellow or pale orange according to the LGBI2 (under Psilolechia lucida not mentioned under Chaenotheca furfuracea). Is it always UV +? Is it likely to be found on the dry bark of an Elm, I suppose it could?

Chaenotheca stemonea: discussed above, should be PD + yellow but unreliable. In this case no Pd reaction detected, including with UV. Is it likely to be found on the dry bark of an Elm, seems unlikely?

Chaenotheca gracilenta: matches in reactions, but LGBI2 says the thallus is greyish green and most internet pictures do show a darker thallus than I have. Positives: it was growing on Elm, its main habitat, and Chaenotheca gracilenta has been recorded from this site perviously.

So no idea what I have: a UV – form of Chaenotheca furfuracea or a pale form of Chaenotheca gracilenta?

Anyone able to help?

Neil
Attachments
Chaenotheca stemonea Mallard Wood, Pd spot test top edge
Chaenotheca stemonea Mallard Wood, Pd spot test top edge
Chaenotheca stemonea Mallard Wood, under UV, Pd spot test top edge
Chaenotheca stemonea Mallard Wood, under UV, Pd spot test top edge
Chaenotheca stemonea Fountains Abbey
Chaenotheca stemonea Fountains Abbey
Chaenotheca sp on Elm, Loftus
Chaenotheca sp on Elm, Loftus
Chaenotheca sp on Elm, Loftus, thallus squash with Stichococcus
Chaenotheca sp on Elm, Loftus, thallus squash with Stichococcus
Neil Sanderson

Dave Lamacraft
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Re: Chaenotheca: a Pd/UV Reaction & a Question

Post by Dave Lamacraft » Mon Mar 23, 2020 7:19 pm

Hi Neil,

I've been scratching my head over a Chaenotheca, in every way fitting stemonea, bar the Pd reaction, which appeared Pd- but on closer inspection (dissecting 'scope) there was a slight yellowing of the thallus as you describe here so that's all good. Interestingly though, I'm not getting a Pd/UV reaction....?

Did you get anywhere with your specimen from Yorkshire?

Cheers

Dave

AlanFUSA
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Re: Chaenotheca: a Pd/UV Reaction & a Question

Post by AlanFUSA » Sat Mar 28, 2020 4:39 am

Hi Neil:
Sorry, can’t help with your sterile crust but glad you enjoyed Kilton Beck. I learnt my lichenology in that area back in the 1980’s when I was living in nearby Brotton. I visited Kilton Beck a few times, but was actually rather disappointed with it compared with some of the other ravines in the area – it appeared too open, which meant it was more heavily polluted than other ravines that had a denser canopy, but perhaps it has improved in the past 30+ years. The best ravine that I found in the area was Saltburn Gill, which, apart from being walking distance from my home, had the added advantage of being a local nature reserve owned and managed by the Cleveland Wildlife Trust, which greatly facilitated access. As well as Inoderma subabietina it also had Bactrospora corticola and Lecania chloratiza as well as several other local rarities. Other ravines in the area supported Arthonia elegans and Thelotreama lepadinum and there were also historical records of Lobarion species, but I never found any sign of them. I had a ms 90% completed on the lichens of these ravines, but life, and me, moved on before I finished it. A comprehensive survey of the ravines of the North Yorkshire/Durham coast would be great project for someone…
Stay safe and healthy - Alan

Neil Sanderson
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Re: Chaenotheca: a Pd/UV Reaction & a Question

Post by Neil Sanderson » Thu Apr 02, 2020 9:04 pm

Alan

Yes I was deeply impressed with what has survived here. The beginning of the Loftus ravine was dull but much better further in. The 2020 BLS winter workshop met further south and had a look at another ravine, May Beck. we were at the upper end of this so a bit different but found, astonishingly Mycoporum lacteum on cliff Hollies, along with Chaenotheca stemonea, Microcalicium ahlneri and Porina multipuncta on Oak, Anisomeridium viridescens on Hazel and Celothelium ischnobelum and Arthopyrenia fraxini on Rowan. As you say, a really good project for someone to take on; what else is in these ravines!

About the Chaenotheca, fairly sure now that this was Chaenotheca furfuracea and that this species is only patchily UV +, from looking at fertile material recently.
Neil Sanderson

Neil Sanderson
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Re: Chaenotheca: a Pd/UV Reaction & a Question

Post by Neil Sanderson » Thu Apr 02, 2020 9:13 pm

Dave
there was a slight yellowing of the thallus as you describe here so that's all good. Interestingly though, I'm not getting a Pd/UV reaction.
Should be OK, the Pd typical produces a black stained mess with the yellow reaction only visible on the edge of the spot in this species. The UV + yellow florescence was not especially strong, just more hat the existing colour is enhanced, which seems typical of yellow to red Pd sections with UV. The UV mainly just makes them easier to see.

As I said above, saddle fairly sure the Chaenotheca species was just UV - Chaenotheca furfuracea.

Neil
Neil Sanderson

AlanFUSA
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Re: Chaenotheca: a Pd/UV Reaction & a Question

Post by AlanFUSA » Sat Apr 04, 2020 1:18 pm

Remarkably, I still have the draft ms for the Saltburn Gill study and it includes data on wind direction from a weather station in nearby Saltburn town. By far the most frequent wind direction is SW, which means most of the pollution from Teesside is blown out over the North Sea (sorry Norway). Westerly winds, which would have blown the pollution to the Saltburn/Kilton area, constitute only 10% of the total!
Alan

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