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The Distribution of Western North American Hepaticae. Endemic Taxa and Taxa with a North Pacific Arc Distribution

1987; American Bryological and Lichenological Society; Volume: 90; Issue: 4 Linguagem: Inglês

10.2307/3243096

1938-4378

Won Shic Hong,

Lichen and fungal ecology

Although there are 75 genera and over 300 taxa ofHepaticae in western North America there are a limited number of endemics. Among these endemic taxa are such isolated, monotypic genera as Geothallus, Gyrothyra, and Schofieldia. These probably originated on the Pacific Plate and Juan de Fuca Plate. Some of the endemics are common and widespread throughout the region, while others are highly restricted to small areas mostly west of the Rocky Mountains. Many are dioicous. Taxa having North Pacific Arc distribution patterns mostly occur from the Himalayan uplands to Alaska and extend southward to California along the North American Pacific Coast in hyperoceanic habitats. The patterns of distribution are provided based on published reports and specimens, including personal collections since 1965. Forty two taxa are endemic in western North America and 23 taxa have North Pacific Arc distribution. Western North America is dominated by the Rocky Mountains, which extend from Alaska to New Mexico, and the Pacific Mountain System. This latter system includes the Coast Mountains which run from southeastern Alaska to southern British Columbia, paralleling the Pacific Coast. The Coast Mountains continue to the north through the Alaskan Range and to the south through the Cascade Range. The hepatic flora of western North America is strongly influenced by Pacific Asian elements rather than eastern North American elements. Schuster (1983) has suggested reasons for this Asian dominance. In particular, during the Cretaceous period, an inland sea divided Laurasia into a western and eastern portion, and isolated a small, western North American area. This area incorporated fragments of the Pacific Plate, whereas eastern North America remained attached to Eurasia. The Rocky Mountains can be divided into 4 regions: 1) Arctic Rockies, 2) Northern Rockies, 3) Middle Rockies and 4) Southern Rockies. The Arctic Rockies include the Brooks Range, Franklin Mountains, Mackenzie Mountains in Alaska, Yukon and Northwest Territories. The hepatic flora of this area was relatively well investigated by Bird et al. (1977), Evans (1901, 1903), Hong and Vitt (1977), Horton (1977), Howe (1899), Persson (1946, 1947, 1949, 1952), Persson and Gjaerevoll (1957, 1961), Steere (1953, 1954), Steere and Inoue (1974, 1975, 1978), Steere and Schuster (1960), Steere et al. (1977) and Steere and Scotter (1978). The Northern Rocky Mountain Trench runs through the Yukon, British Columbia, Alberta and Montana. The hepatic flora of this area is relatively simple and has been investigated by Bird and Hong (1969, 1975), Brinkman (1915, 1923b), Hermann (1969), Hong (1975), Hong and Vitt (1976), MacFadden (1927) and Vitt (1973). The Middle Rockies include the mountains in south central Montana, western Wyoming and north central Utah. The area has been mainly studied by Flowers(1945, 1954, 1961), Hong(1976)and Porter (1933, 1935). The Southern Rockies cover Wyoming, Colorado and New Mexico and has been investigated mainly by Arsene (1933), Evans (1915), Hong (1980c), Shields (1954) and Weber (1963). The richest hepatic flora of western North America occurs in the Pacific Mountain System. This is probably due to variable microhabitats caused by different climates, vegetation, substrata and topography. In spite of variable climatic conditions (including alpine, oceanic, subarctic, humid temperate, semi-arid, arid and mediterranean), only 2 species [Cololejeunea macounii (Spruce ex Underw.) Evans and Hygrolejeunea alaskana Schust. et Steere] of the Lejeuneaceae occur in this area. As pointed out by Schofield (1984), the absence of such neotropical elements in western North America can be attributed to the elimination of broad-leaved forests that in turn prevented the expansion of these elements. This contrasts to the continuation of broad-leaved forests in eastern North America. During the Cretaceous period, western North America was isolated, and evolution of endemism probably occurred here. Even though endemism at the generic and family levels is limited, there are 3 isolated monotypic genera, Geothallus Campbell, Gyrothyra M. A. Howe and Schofieldia Godfrey, restricted to a narrow section of western North America. The hepatic flora of this region was more extensively investigated and published than the oth0007-2745/87/344-361$1.95/0 This content downloaded from 157.55.39.58 on Sun, 31 Jul 2016 05:37:18 UTC All use subject to http://about.jstor.org/terms 1987] HONG: WESTERN NORTH AMERICAN HEPATICAE 345 er areas of western North America as indicated by the works of Brinkman (1923a, 1934, 1935, 1937), Clark (1909), Clark and Frye (1936, 1942, 1949), Cooley and College (1892), Evans (1900, 1901, 1906, 1914, 1923), Frye (1908), Frye and Clark (1946), Fulford (1936a, b), Godfrey (1977a, b), Godfrey and Godfrey (1978, 1979, 1980a, b), Godfrey and Schofield (1979), Griffin and Thurston (1935), Haynes (1909), Hong (1978a, b, 1980b), Horton and Schofield (1977), Howe (1899), Inoue (1965, 1972), Miller and Shushan (1964), Pearson (1921), Persson (1962a, b, 1968), Sanborn (1929, 1941), Schofield (1968a, b, 1984), Schofield and Crum (1972), Schofield and Godfrey (1979), Schuster and Schofield (1982), Stair (1947) and Worley (1970). A total of 42 endemic taxa occur in western North America. Twenty-three taxa of North Pacific Arc distributions occur in this area and are treated in this work. In general, the nomenclature follows Stotler and Crandall-Stotler (1977). The North Pacific Arc species are treated following the western North American endemic taxa. All taxa are arranged in alphabetical order.