Graphis crebra in GB (probably)

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Dave Lamacraft
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Graphis crebra in GB (probably)

Post by Dave Lamacraft » Wed Aug 19, 2020 4:19 pm

I bumped into this whilst working in a woodland on Dartmoor and was instantly reminded of a pic of Neil's Graphis handelii from the New Forest. Whitish thallus, somewhere between scripta and elegans in initial appearance, elegans style 'pursed lips' of young lirellae, but unfurrowed margins on mature lirellae. So, thinking it may well be something interesting I collected some.

Back at home, a K+ yellow turning red thallus (with crystals in a squash, but these took a few goes to get) was pointing in the right direction, and the hymenium was distinctly murky, slightly yellowish, with a few lumps of what look like crystals here and there, so although I find an inspersed hymenium a tricky feature sometimes (distinguishing oil droplets from 'random little bubbles') I was pretty confident in this instance. The spores were also looking pretty thin-walled. So the combination of K+ y to r, inspersed hymenium and thin-walled spores had me reaching for the key in the Portugal paper (link in Neil's handelii post). It got tricky at this point, mostly as the spores - at 34-42.5 x 6.8-8.5 (7-9 septate) - were too big for handelii, according to the paper at least but I've since learnt from Neil that the spores from the Portuguese specimen were smaller than normal, so my spores could fit, but the presence of a light pruina on the discs didn't. I also couldn't decide if the discs were exposed or not, as there was a mixture of both. Either way it was looking like G. cincta or G. crebra, and with help from Neil and Andre Aptroot, it seems like it is Graphis crebra, but it will hopefully get looked at by Gothamie at NHM to be sure.

The pruina seems key to distinguishing handelii and crebra, and adding it in to Neil's key would look something like...

1a Thallus K + yellow to red, producing crystals (norstictic acid) ... 2

1b Thallus K - or K + yellow ... 4

2a Lirellae striate, hymenium not inspersed with oil droplets, spores to 60 µm long ... Graphis elegans

2b Lirellae not striate, hymenium inspersed with oil droplets, spores to 45 µm long ... 3

3a Disc pruinose...Graphis crebra

3b Disc not pruinose...Graphis handelii

4a Spores muriform ... off to Graphis ruiziana, Graphis inustuloides and ‘Graphina’ pauciloculata

4b spores not muriform, three or more septate ... off to Fissurina alboscripta and Graphis scripta s. lat.

It was on a young oak, on a steep slope above a ravine, in quite nice old-growth woodland. Things like Anisomeridium ranunculosporum, Thelotrema lepadinum, Arthonia ilicina, Graphis ruiziana in vicinity

Thanks, as ever, to Neil and Andre for the help.

IMG_1915 (1).JPG
Thallus
IMG_1914 (1).JPG
K+
IMG_1918.JPG
Spore x400
IMG_1925.JPG
Murky insides, with crystal-like bits

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