Hypotrachyna afrorevoluta or revoluta ?

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CJohnsonOHBR
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Hypotrachyna afrorevoluta or revoluta ?

Post by CJohnsonOHBR » Sun Apr 12, 2020 1:43 pm

Hypotrachyna is not common in the Outer Hebrides (5 records of 3 species) and this is the first time I have encountered the genus. So this query will be very short if I'm not looking at Hypotrachnya.
It was collected from North Uist from a coastal conifer plantation and was found on a very small larch twig. I should probably have ignored it, but this is not a good site for lichens, so it was a token gesture of a few randomly collected twigs.
The thallus in 3cm long and wrapped around a twig 2mm in diameter. Pale grey lobes with grey soralia (green when wet). Underside back, shiny with black simple rhizines, some have bifurcate ends. No evidence of cilia.
The soralia are on the edges of the lobes, not restricted to the apices. Sorediate lobes are revolute. There are also some smaller laminal soralia
Cortex K+ yellow, Medulla C+ red.
The description in Nordic Lichen Flora is probably the clearest, but I'm still not sure whether I have T. afrorevoluta or T. revoluta. A perusal of the reliable on-line UK and European sites would lead me to favour T. revoluta.
I think this one for the experts, so comments would be appreciated.
Thank you
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Hypotrachnya-1-copy.jpg
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Hypotrachnya-4-copy.jpg

Mark Powell
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Re: Hypotrachyna afrorevoluta or revoluta ?

Post by Mark Powell » Sun Apr 12, 2020 2:59 pm

My feeling is that you are right with the genus Hypotrachyna and that you are trying to decide between the right pair of species. I am not quite sure I would go as far as saying that you should have ignored it, but it is true that the separation of this pair is best done with well-developed, 'typical' specimens. Young individuals wrapped around twigs are more difficult, as are overly flat and abraded specimens on sawn timber.

I would err towards H. afrorevoluta. One of my reasons is the rather coarse soredia, probably produced in pustular wrinkles and not fine soredia in more even sheets on erect lobes. A character which has only been published by me in the British Lichen Society Bulletin is the difference in rhizines, shades of brown, relatively slender and sinuous in H. revoluta, coarse, jet black and bristle-like in H. afrorevoluta. Yours look more like the latter to me.

If I may, I will provide a link to a twitter thread where I made an illustrated comparison of this pair.
https://twitter.com/obfuscans3/status/1 ... 2998024194

Do ask if you want any further advice with this pair. H. afrorevoluta is mentioned in LGBI2 but the description of it needs considerable revision in my opinion.

Neil Sanderson
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Re: Hypotrachyna afrorevoluta or revoluta ?

Post by Neil Sanderson » Sun Apr 12, 2020 3:31 pm

I agree with Mark that this is Hypotrachyna afrorevoluta and would go further and say the lichen is as near as dammit definitely this.

Did you find this http://wessexlichengroup.org/Species/Hypotrachyna/, a page I put up some time ago on these two species.

Neil
Neil Sanderson

CJohnsonOHBR
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Re: Hypotrachyna afrorevoluta or revoluta ?

Post by CJohnsonOHBR » Mon Apr 13, 2020 8:11 am

Thank you Mark and Neil for clarifying the differences between afrorevoluta and revoluta. I had been oscillating between the two and the more I read, the more uncertain I became. Always a time to seek expert advice. A new species for VC110 and one for the herbarium for future reference.
The next challenge is to find more, preferably large specimens, and to look for the other species. Unfortunately not a tree within walking distance, but I still have my bag of twigs which may produce some more challenges for the novice.

Neil I did find you page on Wessex Lichens, it is very good and has been added to my reference collection.

Many thanks

Christine

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