Having done a bunch of Lichen IDs, I think a lot of the species with very few observations come as a result of lack of observers, and especially observers who have the equipment and desire to go deeper than just a few common foliose ones and start doing chemical tests and microscopy, and that those few of these there are are geographically limited.
Certainly during IDing I’ve seen a lot more issues arising from novices overapplying common species, over-reliance on CV, and uncritical agreements with honest mistakes, than people mistakenly thinking they’ve found something rare or underreported.
I would by no means consider myself an expert nor have I done very much intensive looking at all nor in very exciting places, but I’ve nevertheless managed to find several new species of lichens and lichenicolous fungi new to Denmark (reported to and confirmed on a national site with a more rigorous review process for rare(ly reported) species than iNat). I also have I think 3 that would be new to iNat if I uploaded them here, but I’m somewhat hesitant since I don’t like duplicate reporting. These are:
- Ochrolechia microstictoides - somewhat surprised by this one since it’s widespread and reported as fairly frequent in some places, and not tiny, though with some taxonomic confusion
- Fellhaneropsis myrtilicola - makes sense, it’s sub-milimeter size dots on twigs requiring microscopy, that I only happened to notice because I was looking at something else under a stereomicroscope that happened to also have it
- Stigmidium congestum - also makes sense, barely anyone looks at lichenicolous fungi, even less so little black ones requiring microscopy
- EDIT: actually a fourth one as well, Sarcopyrenia gibba - another little black lichenicolous fungus though one that’s rather easier to find if one knows what to look for than the above one.