Identifying Sterile Biatora vernalis

Another interesting lichen seen in the two SSSIs surveyed in the upper Elan Valley for NRW was Biatora vernalis. This is a widespread species in the central and western Scottish Highlands but is very rarely recorded south of this. This may partly because it is mainly sterile but I does appear to be rare and restricted to high rainfall areas in Galloway, The Lake District, North West Wales and wet areas in mid Wales. It is a species of middle base enriched acid bark on veteran trees, typically in old growth pasture woodlands. When fertile it is distinctive and rather pretty, with orange-brown biatorine (margins and disk the same colour) apothecia, which soon swell and exclude the margin. I have only recently got my head around separating sterile thalli, after seeing fertile material in the Lake District and Wales. The species most likely to be confused with it is the more widespread, if still scarce, Bryobilimbia sanguineoatra (Lecidea sanguineoatra). This is mostly fertile, with black to mottled biatorine apothecia, which do not swell and exclude the margin. Enough sterile thalli of Bryobilimbia sanguineoatra occur, however, to cause confusion.

The thalli of Biatora vernalis are conspicuous wrinkled to verrucose with a lumpy thalli and are quite bright grey-green with yellow tinges. Bryobilimbia sanguineoatra in contrast has a smooth membranous and quite varnish like thallus that forms a continuous thallus. This has a darker grey-green thallus with no yellow tinges.

Photographs (all Elan Valley):

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Fertile Biatora vernalis

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Fertile Biatora vernalis

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A sterile thallus Biatora vernalis, showing the distinctive verrucose nature of the thallus