Heterodermia

[GERAULT]

I am calling on lichenologists who are prospecting at Lizard Point or the Scilly Islands because I have a problem with this taxon from Brittany. In the past, no problem, il was called Heterodermia japonica then Heterodermia propagulifera but the French and British authors currently disagree on the name to give to this taxon from Brittany, the Scilly Islands and the Lizard. For the moment I have retained the name Heterodermia neglecta = Polyblastidium neglectum according to the French autors but it complicated because i have just found, on a cliff very exposed to seawater projections, a form with abundant isidium-like growths. Have you already encountered this taxon ? and do you have an idea of the name to give it?
Thank in advance.
Alain

[Neil Sanderson]

Gerualt

This is opportune, as I am working on a project in the Lizard currently, although the main field work is now finished (the work is advising and monitoring on the lichen interest for a large-scale land management scheme aiming to shift the Lizard back to its early 20th C base line condition, much more grazing and prescribed fire, with the latter requiring fire refuges re-established around sensitive rock outcrops first), but I am now familiar with what we call Heterodermia speciosa there. I have not been to the Scilly Islands, but the LGBI 3 is clear that the Scilly Islands taxa is not the same one and we call that one Heterodermia propagulifera, with the former having a corticate lower surface and the latter having a non-corticate lower surface. Paul could probably elaborate on this better than me.

However, as noted in LGBI, our Heterodermia speciosa is very atypical in producing farinose isidia in the centre of the thallus (check GBIF photos of Heterodermia speciosa, none have this feature). The LGBI 3 comments:

it should probably be considered a separate, endemic species

Obviously more work is needed. If it is an endemic taxa then my recent survey found it in 17 individual locations, which is the entire known population, so collection would need thought and permission. It looks like you may have the same taxa as the Lizard Heterodermia speciosa. Photos:

"Heterodermia speciosa" at Kynance, Lizard

Habitat, on ledge (with grossly over grown and scrub invaded heath beyond, one of the areas being tackled by the project)

More "Heterodermia speciosa" thalli (note threatening Bramble at base of picture)

Neil

PS It would be worth looking out for Cladonia stereoclada in that habitat, that was found new to England in the Lizard and then West Penwith during this project

Cladonia stereoclada, West Penwith

Neil

[Paul Cannon]

I agree with Neil, your lichen looks very much like H. speciosa. However, the names of none of the British species are really well understood. Holger Thüs from Stuttgart is working on the group and I'll point him towards your post, he may be able to add more. I worked with him a few years ago on the problem and we made a poster - see this link - https://1drv.ms/b/s!AtAZzqK1uC9ChsVVRen ... g?e=YXfDsn.
Best wishes
Paul

[HolgerT]

Dear Alain, Neil and Paul,
we do have already genetic data for this lichen from two different herbarium collections from the Lizard. There is no need to decimate that very small population any further. The sequence data from the two collections are identical and the taxon is only remotely related to the true H. speciosa (we now have also a good amount of reference sequences for the true H. speciosa from various parts of the Alps).

I had access to previous collections preliminary labelled as H. speciosa from Brittany which genetically turned out to be in one of the H. japonica-like clades. It is clearly neither the true H. speciosa nor the H. speciosa auct. britt. from Cornwall. Your new observation in Brittany however looks different to the previous one and I agree, it is very similar to the Cornish lichen. It would be wonderful to test if this is a second population of the lichen originally known only from Cornwall. I would be very happy to sequence it, if you can provide a small fragment of this lichen.

I will send you a mailing adress in a separate message.

best wishes
Holger

[GERAULT]

I have forwarded to Holger a piece of the taxon presented here, the P+ orange staining (presence of nortistic acid) and the ITS sequencing indicate that it is a form of Heterodermia propagulifera.
Thanks Holger.
Alain