Graphis handelii
An apparently rare Graphis, one of several pan tropical species recently found in Europe. In this case possibly over looked rather than recent a colonist as it has only been found in high quality lichen rich sites. Can be spotted by the somewhat more erumpent non-striate lirellae on a pale grey thallus and definitively distinguished from Graphis scripta s. lat. in the field by the K+ yellow→red spot test. In section confirmed by the hymenium being inspersed with oil droplets and a K+ yellow→red (crystals) reaction in the thallus, indicating the presence of norstictic acid (as with G. elegans). So far found on Hazel stems in an Atlantic Hazel wood in The Burren, Co Clare and on acidic bark on veteran Holly and Beech in old growth pasture woodland in the New Forest.
Similar to Graphis scripta (i.e. with non-striate lirellae), but the thallus has a K+ yellow→red (crystals) reaction (as with G. elegans), and the hymenium is inspersed with oil droplets and ± exposed in mature ascomata. Mature ascospores of British material measure 25–45 × 7–9 μm and are 6- to 9-septate, smaller poorly formed spores also typically occur, the smallest measured being 17 x 6µm and 5 septate.
A pantropical species but recently reported from Portugal (there with rather smaller ascospores; illustrated by Lepista & Aptroot 2016) and now west Ireland and S. England. Potentially overlooked for G. scripta s. lat., or for apparently young specimens of G. elegans. The lirellae of G. handelii often partially fall out, with new lirellae regenerating in the scar; this can give the impression of striate lirellae as found in G. elegans. Graphis crebra is similar but has pruinose hymenia and has been recorded in Devon.
So far recorded from Hazel, Beech and Holly in southern old growth oceanic woodlands, potential more widespread.
First collected from Hazel in an Atlantic Hazel wood in the Burren, Co Clare in 2009, but identified only recently. In 2021, also found on the acid bark of older Holly and Beech in the New Forest in old-growth woodlands (S. Hampshire).
Not evaluated, but probably at least a Notable species, potentially a Red List species.
Aptroot, A., Weerakoon, G., Cannon, P., Coppins, B., Sanderson, N. & Simkin, J. (2023). Ostropales: Graphidaceae, including the genera Allographa, Clandestinotrema, Crutarndina, Diploschistes, Fissurina, Graphis, Leucodecton, Phaeographis, Schizotrema, Thelotrema and Topeliopsis. Revisions of British and Irish Lichens 36: 1-23.
Text by Neil A Sanderson based on Aptroot et al (2023)