Geographic patterns of genetic variation in Pinus monticola

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Genetic differentiation of 59 populations, representing the geographic distribution of Pinus monticola, was studied in field, greenhouse, and laboratory tests. Geographic variation was described by regression models, which accounted for as much as 85% of the variance among populations. Populations from the north (Rocky Mountains, northern Cascades, and northern coastal areas) are generally of high growth po- tential and low cold hardiness. Southern populations (Sierra Nevada) exhibit low growth potential and high hardiness. Populations from the central and southern Cascades are arranged along relatively steep latitudinal dines that connect northern and southern groups. Although differentiation within the transitional region was readily detected, patterns of variation within northern and southern regions were either weak or nonexistent. Nowhere was genetic variation related to the elevation of the seed source.