The Lichen Genus Coccotrema in North America

Two species of the genus Coccotrema (syn. Perforaria) are reported from North America, both from the west coast. Coccotrema maritimum sp. nov. is restricted to maritime rocks, and C. pocillarium (Cumm.) comb. nov. is a sorediate species found mainly on tree bark and wood. A discussion of possible phyto- geographic connections in the Pacific basin is presented together with descrip- tions and illustrations of both species. On the west coast of North America, there are two species of the genus Coccotrema, a genus which has its centre of distribution in the southern hemisphere. One of these species grows abundantly in the Queen Charlotte Islands, British Columbia, on sea coast rocks subjected to salt spray. Morphologically, it appears to be very closely related to C. cucurbitula (Mont. in Gay) Miill. Arg. Its ecology is quite distinct from that species, however, which is never found on maritime rocks. Its chemistry also differs from that of the type of Pertusaria cucurbitula Mont. in Gay. In view of these facts, it is here de- scribed as new under the name Coccotrema maritimum. The other Coccotrema is also abundant on the Queen Charlotte Islands, but is known from Oregon to Alaska. It is a very conspicuous corticolous lichen along the coast and had been described as new by four different authors. Merrill named some material from Vancouver Island as Pertusaria carnea for Macoun's exsiccata, Canadian Lichens, but he never validly published it. Magnusson (1939) put the species into the genus Ochro- lechia, calling it 0. pacifica, based on material from Oregon. Howard (1970) treated it as such in her revision of the genus. Degelius (1937) correctly referred this species to the genus Perforaria (a synonym of Coccotrema) and named it P. minuta. However, it was in Cummings' treatment of the lichens of the Harriman Alaskan Expedition in 1904 that the first valid publication of the species was made, as Pertusaria pocillaria. Coccotrema was circumscribed by Miiller (1889a) based on a new species, C. ant- 1 thank Drs. Rolf Santesson and Henry Imshaug for their comments, suggestions, and criti- cisms. I also thank Dr. Vernon Ahmadjian for culturing and identifying the thalline and cepha- lodial phycobionts, Mr. Martyn Dibben for performing chemical studies on the type of Pertusaria pocillaria and for bringing additional North American specimens of Coccotrema to my attention, the curators at G and PC for the loan of critical types, and Dr. Robert A. Shoemaker for his photographs of Coccotrema as well as his helpful discussion of the mycological aspects of the problem. Dr. John Gillett helped with the Latin diagnosis. 2 National Museums of Canada, Museum of Natural Sciences, Ottawa, Ontario.