Stereocaulon from roofing felt

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JonasRavn
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Stereocaulon from roofing felt

Post by JonasRavn » Mon Jun 08, 2020 5:38 pm

Hello everyone,
This Stereocaulon was found in northern jutland, Denmark and as the title says it was growing on roofing felt. It was sent to me by a user of one of the national citizen-science portals (www.fugleognatur.dk), and I am having some issues identifying it.

There were samples from 4 thalli in the parcel, all from the same location and substrate. One of these was a characteristic S. dactylophyllum, but the remaining deviate from this quite a bit both in the shape of phyllocladia and in the thickness of tomentum. It is also P+ orange, however. Going through Lamb's key for the arctic and boreal species I tentatively arrive at S. dactylophyllum var. occidentale, but the phyllocladia are very variable within the same thallus and I can't find any photographs of this taxon online to compare, so I am very uncertain.

Any thoughts or comments on the ID or how to proceed are more than welcome.

-Jonas

Stereocaulon cf. dactylophyllum (tagpap, Gerth) 1-1s.jpg
Overview of the thallus; pseudopodetia < 2 cm and they are distinctly dorsiventral



Stereocaulon cf. dactylophyllum (tagpap, Gerth) 1-2.jpg
Stereocaulon cf. dactylophyllum (tagpap, Gerth) 1-3.jpg
Stereocaulon cf. dactylophyllum (tagpap, Gerth) 1-4.jpg
Stereocaulon cf. dactylophyllum (tagpap, Gerth) 1-5.jpg
Close-ups of phyllocladia - I have tried to capture some of the variation within a single thallus



Stereocaulon cf. dactylophyllum (tagpap, Gerth) 1-6.jpg
Lower surface

Neil Sanderson
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Re: Stereocaulon from roofing felt

Post by Neil Sanderson » Wed Jun 10, 2020 5:06 pm

Jonas

I am not very experienced with Stereocaulon species, so can not give a definite answer, but it looks like in the last picture the lower surface of pseudopodetia is thickly tomentose, which would rule out S. dactylophyllum. The LGBI 2 says this is
usually without tomentum on lower surface, very rarely slightly tomentose towards base of young branches
In the LGBI 2 key this would come out as S. tomentosum on the information given, but if this is a likely identification I have no idea.

Neil
Neil Sanderson

JonasRavn
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Re: Stereocaulon from roofing felt

Post by JonasRavn » Fri Jun 12, 2020 12:04 pm

Hi Neil,

Thank you for your reply. You are right that the lower surface is quite thickly tomentose, but I am not sure whether or not this is sufficient to rule out S. dactylophyllum. One of my many challenges with Stereocaulon is the frequent use of terms such are "more or less", "usually" and the likes in the keys and descriptions. Furthermore the descriptions are not always consistent between different keys. Some sources state, as you mentioned, that S. dactylophyllum should be more or less glabrous, but in "Lichens of Finland" (Stenroos et al.) it described as "more richly tomentose" than S. subcoralloides.
The picture of the lower surface shows the tip of a pseudopodetium, but most of the bases are covered in some sort of "gunk" from the substrate, and evaluating anything on them is quite tricky. I will try to get some fotos of an entire pseudopodetium for comparison, when I get home from a trip in a week's time and follow up in this thread.

Best regards,
Jonas

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