Athallia from Aarhus, Denmark

Hello Jonas, welcome to the forum.

I’m no expert in these lichens, but Ulf’s paper says that A. holocarpa is rare on bark (commoner on wood), and when it does it is close to the ground. If that does not match your habitat and the hypothecium measurements are OK, then I guess you have cerinelloides. It’s not easy to judge this last point from your image as it appears that algae are obscuring the hypothecium. Or is there really a continuous layer under the apothecium?

Best wishes

Paul

It is nearly a year since this query about Athallia was posted. Forgive me if I revert to ‘Caloplaca‘ for the purposes of this post. The apothecia are not quite as closely packed and even-sized as I would expect in C. holocarpa or C. cerinelloides. In addition there appears to be a thalline margin which, while becoming rather excluded at a fairly early stage, makes this material very reminiscent of C. pyracea. When the 2009 ‘Flora’ was published, C. pyracea was considered a rarity, a specialist of Scottish aspen. Since then it has been found widely in England, mainly but not exclusively on aspen. You will see from this tweet that I found it on a London Plane in Exhibition Road, near the Science Museum.

https://twitter.com/obfuscans3/status/1002486071379267586

Your photo shows apothecia which are a bit paler than the more typical shades of orange but the morphology is very much like C. pyracea and I think you should perhaps consider this possibility.

Although the younger apothecia in your photo are rather yellowish for pyracea, I am placing more weight on the morphology. The apothecia in various individual Athallia species can be rather variable in colour. In the following close-up from your photo, we can see rather scattered (not closely packed) apothecia with fairly well-developed patches of grey thallus and a grey thalline margin.

[attachment=0]Screenshot 2021-03-01 at 10.15.05 AM.png[/attachment]
The usually scant thallus of A. holocarpa consists of tiny orange blobs and the apothecia have entirely orange margins (including the thalline margin). The thalline margin of A. cerinella is grey but usually hardly apparent and the apothecia normally closely packed. I am rather dubious about my few previous records of A. cerinelloides and now think that specimens I originally named as such should be considered as corticolous A. holocarpa. I sometimes find A. holocarpa on smooth bark of twigs and small branches of hybrid Black Poplars.

Although there is not much in your photo to judge the size of the apothecia by, the little lobes of ciliate Physcia make me think that they are rather large for A. cerinelloides or A. holocarpa.

We will have to leave this as unresolved but hopefully the discussion has raised your awareness of pyracea.