Lichenologist is a specialist (e.g., researcher, museologist) studying lichens.
There are several hundred of lichenologists of the world.
(Detail from the diaries of Susanne Anne Moodie, c. 1800)
"I could not help laughing at this odd little man; for it was not the beautiful blossoms, such as you delight to paint, that drew forth these exclamations, but the queer little plants which he had rummaged for at the roots of old trees, among the moss and long grass. He sat upon a decayed trunk, which lay in our path, I do believer for a long hour, making an oration over some greyish things, spotted with red, that grew upon it, which looked more like mould than plants, declaring himself repaid for all the truoble and expense he had been at, if it were only to obtain a sight of them. I gathered him a beautiful blossom of the lady's slipper, but he pushed it back when I presented it to him, saying: "Yes, yes;'tis very fine. I have seen that often before; but these lichens are splendid."
I never pursued a deer with such earnestness as he continued his hunt for what he called "specimens"."
(Richardson (1975): The vanishing lichens)
On the homepage of IAL (International Association for Lichenology) you can find lists of lichenologists and societies of lichenologists, as well as issues of the International Lichenological Newsletter (ILN) containing valuable information on lichenology and lichenologists.
Who studies them?
Institute of Ecology and Botany, Centre for Ecological Research,
Hungarian Academy of Sciences, H-2163 Vácrátót, Hungary