Hello, I would like to know if the lichen on the twig in the photo is X. polycarpa or parietina, I suppose it is one of the two. How is it possible to separate the species in the field, or is a microscope necessary? (This is from Greece). Many thanks for your help! dion
Hi Dion, Lovely lichen! The substrate, shade and presence of apothecia suggest X. polycarpa, particularly if tree is hardwood and the environment is nitrogen rich, eg. close to urban area or other reasons. I can eliminate X.candelaria, X. elegans and X. fallax because of habitat and visible characters, but I don't know X.parietina, so cannot comment on that. Also, I'm in the PNW of NA, and there may be other species in Greece with these characters. If this were PNW I'd feel somewhat confident without microscopy, but anywhere else, who knows. cheers! frog