Notes: Lecidea atrobrunnea is a rather variable taxon, especially its gross morphological characters (Hertel and Leuckert, unpubl.). In the area of investigation, which is outside its center of its diversity, we found the following subspecies, which are mainly characterized chemically: subsp. atrobrunnea (with confluentic acid and/or 2'-Omethylperlatolic acid), very common in high montane and alpine belt; subsp. saxosa (with norstictic acid syndrome), a less common taxon, restricted in this area to high elevations (San Francisco Peaks, San Bernardino Mtns.); and subsp. stictica (with stictic acid syndrome, occasionally with hypostictic acid), a relatively rare taxon, restricted to higher elevations and with a tendency to prefer more continental climates. The contrast between the conspicuous black prothallus and apothecia to the brown thallus areoles may have caused Ramond to create the epitheton "atrobrunneum" (Latin: black-brown). upper surface: usually pale brown to more rarely dark reddish brown in the center of areoles, shiny lower surface: dark (only to be seen in some squamulous specimens) Note: Chemically Lecidea atrobrunnea subsp. stictica is somewhat aberrant, in containing (beside some stictic acid), also 2'-O-methylperlatolic acid and norstictic acid in small amounts (by TLC).