pf339's picture

Parasitic lichen?

Observed: 22nd June 2012 By: pf339
S159 Neighbourhood Nature - course complete
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Parasitic lichen i
Parasitic lichen ii

Grey areolate crustose lichen with dark prothallus (possibly Aspicilia caesiocinerea) growing on siliceous rock seems to be being taken over by a larger structured light yellow crustose lichen with bigger areoles and with black apothecia. Parasitic lichen possibly Rhizocarpon viridiatrum.


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Species interactions

No interactions present.


AlanS's picture

I don't think so.

It does look as though one lichen is invading, overgrowing or parasitising another. Defintely two lichens there with different apothecia, and that with the larger areoles and apothecia could well be a Rhizocarpon.

But I don't think it is R. viridiatrum, which is fairly bright yellow like R. geographicum and R. lecanorinum. Even allowing for the fact that digital cameras are often very poor at recording pale yellow in lichens, I cannot reconcile the photos with R. viridiatrum, in either colour or morphology. Nor is the being-invaded lichen Aspicilia caesiocinerea, the usual host of R. viridiatrum. [Might be a Fuscidea?]

I have a feeling I should know what the main subject is, but no firm suggestion at present. [Still in coffee-assimilation mode here.]


pf339's picture

Thanks for help

Interested in beginning to see extra possibilities. I looked at this for a long time trying to see where the larger structures might be developing from the smaller areoles. Finally realised might be two completely different lichens and that led to suggesting possibility above. Thanks for help.

pf339's picture


Thanks for your help considering this lichen and especially for returning to it. Much appreciated.
Sometime this year I hope to return to the Stiperstones and spend more time to look at things more closely. I think I have a good idea of the patch of rocks where I saw this lichen so shall certainly try to find it again and take more pictures.

AlanS's picture

I agree,

It is an interesting site.

I was there on a botanical meeting a year or so ago, didn't have time to look much at the lichens (though a rare Cladonia, subject to my checking it, which I still haven't done).