Mystery lichen on sandstone church wall

A little-known feature of the genus Solenopsora is that it has the distinctive ‘computer mouse’ haustoria which are also seen in Catillaria, Halecania and Leprocaulon. In the following drawing, Lepraria lobificans (lacking such haustoria) is provided for comparison with Leprocaulon calcicola as these two leprose lichens look almost identical in the field and the presence of such haustoria is one of the characters I use in confirming specimens of L. calcicola.

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It has been fascinating to see these four genera jumping about in their higher taxonomic placements, variously placed in different families and even in different orders. LGBI3 currently places Catillaria and Solenopsora in the Catillariaceae and Halecania and Leprocaulon in the Leprocaulaceae, both those families in the Caliciales. LGBI2 considered Catillaria, Halecania and Solenopsora to belong in the Catillariaceae and placed this family in the Lecanorales. In the meantime, at one stage Halecania and Leprocaulon were together in the family Leprocaulaceae which was placed in a newly erected order Leprocaulales. A relatively recent paper has transferred Solenopsora to the Leprocaulaceae.

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A note has been placed in the LGBI3 account for the Leprocaulaceae to explain the higher taxonomic placement used there.

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Surely Catillaria, Halecania, Leprocaulon and Solenopsora will all end up in the same family eventually? Catillaria and Halecania seem so similar in so many respects that I can’t believe that they belong in different families.

Anyway, this is not necessarily relevant to the interesting lichen on Petworth Church but many colonies of Solenopsora vulturiensis are likely to be sterile and less well-developed. It made me think that if I had a some suspected S. vulturiensis that I wasn’t sure of, I would certainly examine the photobiont cells to see if any of the distinctive haustoria were present (and it might be useful for someone who has access to this species to check that the haustoria are indeed easily apparent in that species, I have only looked for them and seen them in S. candicans).

I notice that the LGBI3 account for S. vulturiensis doesn’t mention its occurrence on walls and this might be disconcerting for anyone thinking they had found it in churchyards. Some Continental accounts, including the lichensmaritimes and Italic websites, include chapels and walls in habitat notes for S. vulturiensis.

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I start to feel a little jealous when I think of such exotic species as Solenopsora vulturiensis in churchyards. However, this is probably partly a case of ‘the grass seeming greener on the other side’ because the churchyards of my home region (South Midlands and northern Home Counties) do seem genuinely surprisingly rich in a national comparison. The list for my own relatively unremarkable parish churchyard, chosen at random by fate simply because I live here, now has a list of over 160 (plus 15 lichenicolous fungi). It has been an interesting exercise to keep working away at a single churchyard and to compare these results with what is found in typical one-off visits. Here are some observations.

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When I revisited some of the sites that Jack Laundon studied in the 1970s, his annotated species lists were particularly interesting because they provided a subjective assessment of abundance. I am producing something similar for the main sites in my parish; here is the first part of the churchyard list.

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