| Summary: | Bryobrittonia pellucida was first described by R. S. Williams from sterile material collected in April 1899 on a bluff of the Yukon River, just below Dawson City, Yukon Territory. This species, which Williams placed in the monotypic genus Bryobrittonia, was considered for several decades to belong in the Pottiaceae. In 1953, Steere described sporophytes from specimens collected in the Brooks Range, Alaska. The presence of large, campanulate calyptrae .; erect, 8-ribbed capsules; and double peristome are all characters of the Encalyptaceae. As Steere pointed out, Bryobrittonia should be placed in this family and retained as a genus separate from Encalypta. . In the summer of 1973, while collecting in the Grande Cache region, north of Jasper National Park, Alberta, Wilbur Peterson and the present author found Bryobrittonia pellucida in quantity along a small stream at Sherman Meadows, about 150 km. south of Grande Prairie. Later in the summer they collected the species along small streams in the Yukon Territory in the Whitehorse area, and with sporophytes at Dawson City and in the Mt. Klotz region of west-central Yukon. In 1972, collections were obtained from the Kluane Lake region of southwestern Yukon. All of the collections were from sandy silt banks beside streams. The Alberta collections were from 1220 m. elevation in an area of Pinus contorta and Picea glauca in the upper montane zone and are approximately 900 km. south of its previously known range. . After Williams made his collection at Dawson City, Bryobrittonia pellucida was not rediscovered until Persson published details of two collections from the Seward Peninsula, Alaska. Steere reported numerous collections from the Brooks Range, Alaska, as well as Coppermine, N.W.T., and Prince Patrick Island in the western Canadian Arctic. It has also been reported from Peary Land in northern Greenland, northern Ellesmere Island, and Axel Heiberg Island. Brassards added an additional locality on northern Ellesmere. Savicz-Ljubitzkaja and Smirnova recorded it as occurring in the Polar Urals and eastern Siberia (probably near the Lena River). Examination of material in the National Museum of Canada has revealed additional locations of the species in the Nahanni River region of the southwestern Mackenzie District, the Mackenzie River delta in north- western Mackenzie District, and in the Kluane Range region of southwestern Yukon Territory. The distribution of Bryobrittonia pellucida, as it is presently known in North America is shown on Fig. 2 and its altitudinal range along the western cordillera in Fig. 3. . Although the presence of these species in disjunct localities in the alpine or upper montane zones of the Rockies may be the result of recent long distance dispersal from more northern populations, it seems more likely that these species survived at least the Wisconsin glaciation in situ in refugia, far south of their continuous Arctic range. The importance of alpine refugia has been long underrated in North America and it is likely that many of the arctic circumpolar species will be found in alpine habitats of western Alberta, northwestern British Columbia and particularly in the unglaciated alpine regions of the Yukon.
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