Littoral Species of Caloplaca in North America: A Summary and a Key

A total of 20 species of Caloplaca have been found to occur, obligately or occasionally, in the littoral and supralittoral zones on seashore rocks in continental North America. Eighteen species are marine to maritime and two are mainly inland species with occasional occurrence on the shore. On the west coast there are 16 species occurring on seashore rocks, while the east coast contains only five species. Europe and North America share 40% of the littoral species. A total of 12 species seem to be endemic to western North America. None of the 18 marine to maritime species is known to occur also in the southern hemisphere. A key, a short description for each of the treated species, and statement of their distribution is given. The species are also depicted in color photos.