Physcia dakotensis
Physcia dakotensis is a species of saxicolous foliose lichen in the family Physciaceae. It was formally described as new to science in 2004, based on specimens collected from granitic rock in South Dakota, USA. The lichen forms small, tightly, leaf-like thalli with narrow gray that produce distinctive coarse, upright soredia, and it was initially mistaken for the eastern North American species P. subtilis. It is distinguished by its highly fissured morphology, poorly developed lower with sparse rhizines, and K-positive cortex containing atranorin.
Taxonomy
Physcia dakotensis was formally described as new to science in 2004 by Theodore L. Esslinger, who published the and Latin protologue in Mycotaxon. The holotype was gathered on July 25, 1996, along State Highway 25, just south of Lake City, Marshall County, South Dakota, where the lichen was growing on hard, acidic granitic rock.Esslinger coined the specific epithet dakotensis to reflect the Dakotan prairie where the species was first encountered during fieldwork that began in 1975. For years the minute, rock-dwelling thalli were mistaken for the eastern North American P. subtilis, but closer study revealed a distinctive set of characters: tightly, highly fissured lobes that develop coarse, upright soredia; a poorly developed lower cortex with few or no rhizines; and a K-positive cortex producing atranorin. Taken together, these traits warranted recognition at the species level and set P. dakotensis apart from all previously described North American members of the genus Physcia.