Variation and climatic adaptation in northern populations of Datura stramonium
Between- and within-population variation for 21 quantitative characters was estimated for five populations of Datura stramonium originating along a climatic gradient ranging from southern Ohio, U.S.A., to Elgin County, Ont., Canada. Datura stramonium is a predominantly inbreeding, annual species with a distribution which is expanding northward in Ontario. Plants were grown from seed to maturity in the greenhouse under uniform conditions. The five populations differed significantly in the mean values of all measured characters. Canonical variates analyses were used to distinguish the populations on the basis of combined groups of characters. Canonical means of the five populations differed significantly for both seedling and mature plant characters, but the relative distance between populations varied for the two character sets. Levels of between- and within-family variation differed significantly among populations and from one character to another. Percent germination, seedling dry weight, and leaf area were strongly correlated with initial seed weight. Seed weight and cotyledon length increased and days to anthesis decreased with a decreasing length of the growing season.