Lecanora hybocarpa crystals

Dear Sylvia —

Many thanks for sharing this Lecanora. I’ve found one like that as well, on a birch twig that I collected in Argyll last summer. I posted a Twitter thread about it — please see https://twitter.com/specanatura/status/1740325933310214160” class=”bbcode_url”>https://twitter.com/specanatura/status/1740325933310214160. I believe Jenny Seawright has seen a similar Lecanora as well.

If you haven’t done so already, I’d recommend testing with Pd to determine whether you have the usual form of L. pulicaris.

You may well do, as L. pulicaris prefers lignum or clean acid bark. In contrast to L. hybocarpa auct. br., L. pulicaris has fine (not individually discernible at <400x magnification) epithecial granules descending between the paraphyses. If your lichen is L. pulicaris, the thalline margin in particular should give a red reaction due to fumarprotocetraric acid.

However, research in mainland Europe (Malicek, 2014) has shown that approximately 15% of L. pulicaris specimens lack fumarprotocetraric acid and give a Pd- test. This chemotype has not been reported from GB&I, but it may exist here. The only way to be sure would be to subject your specimen (or mine, or Jenny’s) to lab testing (TLC or DNA barcording).

In the meanwhile — and assuming you don’t have the usual Pd+ red L. pulicaris, of course — it would be possible to record your specimen as Lecanora sp., keeping the photos for future reference and study.

As for your crystals in K, though — it seems from your photos that you’re referring to the calcium oxalate crystals in the thalline margin? These crystals don’t dissolve in K, whereas the epithecial granules do.

The Lecanora genus undoubtedly has more surprises in store for us British lichenologists! Indeed, I’m personally a bit unsure of our British Lecanora species concepts, which I believe Neil Sanderson’s elucidation of L. hybocarpa auct. br. has called into question somewhat. For more on that if you’re interested, please see my recent Fungi Forum post (to which I intend to add some future posts once time allows) — https://www.fungi.org.uk/viewtopic.php?t=4225” class=”bbcode_url”>https://www.fungi.org.uk/viewtopic.php?t=4225.

Best regards,

Anthony

Dear Sylvia —

Thanks for your reply. I was about to send a follow-up to mine, as I saw that I may have misunderstood you in my excitement that another potential L. pulicaris of the Pd- chemotype might have been found!

The epithecial granules in your first photo seem discernible at that magnification, which I assume is 100x or so. That suggests it may not be L. pulicaris of either chemotype. But it’s perhaps worth checking with Pd, as it does seem to have a bit of the L. pulicaris ‘look’ about it, and it’s on lignum. (Perhaps the substrate isn’t entirely significant, assuming the wood is highly eutrophicated. It probably must be to host L. campestris, which I believe doesn’t like acid substrates).

It doesn’t seem the most typical example of L. hybocarpa auct. br. — normally the coarse, descending granules are more abundant, at least in my experience! But it’s also not clearly L. chlarotera s. str either. Some of the granules may have smeared down with the blade — i.e. those scattered deep ‘in’ the hymenium that don’t form a ‘chain of crystals’ back up to the epithecium. A test with Pd, and a section from another apothecium to check the crystals, might help.

As for the calcium oxalate crystals — I haven’t seen them like that myself, but I suspect it’s possible for them to take that elongated form, if they’re deposited as the thalline margin grows. So far as I know, no distinction is made in the shape of the thalline margin crystals, but only their size (e.g. small for e.g. L. campestris and L. horiza, and large for e.g. L. pulicaris and L. hybocarpa auct. br.).

Sorry I can’t be more definitive! Maybe someone else has some insight.

Best regards,

Anthony