Members of this group are most diverse in mountains of the continental western United States and Alaska.

It is found in the Rocky Mountains, including in alpine zones,[citation needed] and in the United States Sierra Nevada range.

[4] The Lecidea atrobrunnea species complex has been the subject of extensive study due to its vast diversity, particularly in western North America.

The complexity of this group is highlighted by the morphological and chemical variability that masks its true biodiversity.

This finding challenges previous assumptions about the monophyly of commonly occurring taxa like L. atrobrunnea, L. protabacina, and L. syncarpa in montane habitats of western North America, which are now shown to be polyphyletic.

The research also reveals narrow geographical distributions for many of these candidate species-level lineages, although sampling is still incomplete.