Ochrolechia parella/pallescens on trees

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Neil Sanderson
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Ochrolechia parella/pallescens on trees

Post by Neil Sanderson » Sat May 11, 2019 8:45 pm

Late last month Andy Cross and I were doing some vascular plant recording for Atlas 2020 on the New Forest near Ipley. Not finding much new, we strayed in to a small area of pasture woodland, which had some wood edge veteran Oaks. These are quite rare in the New Forest as the general expansion of the woodlands 150 years means most veteran trees are imbeded with the woods. We did not find much until the last Oak we looked at, which had what I thought for a little bit was some very well developed Varicellaria velata, but I then twigged was Ochrolechia parella s. lat. confirmed by the disk reacting C + red. In Varicellaria velata,only the apothecia margin is C + red. In the New Forest the Vulnerable Varicellaria velata, is actually quite widespread but epiphytic Ochrolechia parella s. lat. is actually very rare, with only one other record.


A thallus of Ochrolechia parella s. lat. on old Oak, Ipley, New Forest

A closer view of the thallus Ochrolechia parella s. lat. on old Oak, Ipley, New Forest

(Pictures by Andy Cross)

Ochrolechia parella s. str. is a common species of some what nutrient enriched acid rock, but it is locally rare in the New Forest area due to lack of habitat. Material occurring as an epiphyte was called Ochrolechia pallescens but this taxa was dropped in Britain as there were no relabel morphological differences with Ochrolechia parella s. str. However, on continental Europe recent DNA sequencing suggests that the epiphytic material in parts of Europe is actually a separate cryptic species https://herzogia.blam-bl.de/images/Herz ... lechia.pdf, which is quite a rare species in some countries. The situation in Britain is not clear as some epiphytic Ochrolechia parella s. lat. is found adjacent to saxicolous material and is presumably Ochrolechia parella s. str. and no-one appears to have sequenced British material. This New Forest material, however, looks like a good candidate for true Ochrolechia pallescens, as there is no Ochrolechia parella s. str. anywhere near this. If it was, it would be new to Britain, but I would need to get it sequenced to prove this. Anyone out there able to sequence this?

Neil Sanderson

Dave Lamacraft
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Re: Ochrolechia parella/pallescens on trees

Post by Dave Lamacraft » Thu Jun 20, 2019 7:32 am

That's interesting, thanks Neil. Ochrolechia parella isn't that unusual on trees around me, I remember one specimen on sycamore showing a C- reaction with the disc, presumably the pruina, whilst the epihymenium was C+ red (visible in a section), a feature mentioned as occurring in both species in the O. pallescens account in the paper. I remember Steve also suggesting the possibility that a putative record of Pertusaria coccodes of mine from a lone ash on a coastal heath could be P. pseudocorallina that had crept from rock to tree. Anyway, I can collect corticolous specimens of O. parella if anyone wanted material for sequencing.

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