Green foliose lichen

Dear Francesco —

Many thanks for your post, and your interest in lichens.

It’s often difficult to identify a lichen from just one or two photos. I’d be willing to wager, though, that your lichen is either Flavoparmelia caperata or F. soredians. The yellowish colour of the thallus, especially in the centre, would be characteristic of these species, separating them from other similar ‘parmelioid’ lichens.

The reproductive structures on your lichen are soredia, not isidia. Isidia have a cortex, so they don’t look as ‘powdery’ as soredia. The soredia of F. caperata and F. soredians tend to form on the revolute ‘folds’ of the lobes, where they become confluent. That seems to be the case with your lichen.

It’s not really possible to be certain of which species you have from these photos. There are some differences, but the two species look quite alike. In the UK generally, F. soredians is less common, but it depends on the location. A chemical test using K (potassium hydroxide) would be necessary to separate them definitively: the medulla and soredia of F. caperata would be K-, while those of F. soredians K+ yellow turning red.

For more detail, see https://britishlichensociety.org.uk/sites/default/files/Flavoparmelia%20caperata.pdf” class=”bbcode_url”>https://britishlichensociety.org.uk/sites/default/files/Flavoparmelia%20caperata.pdf.

Best regards,

Anthony