Variation Among Individual Seed Masses in Lomatium Grayi (Umbelliferae) Under Controlled Conditions: Magnitude and Partitioning of the Variance

Although seed masses are generally believed to be fairly constant within plant populations and important in plant demography, there have been no studies that quantified the magnitude and partitioning of variation in individual seed masses within and among total seed crops of uncultivated plants grown under similar conditions. In lomatium grayi (Umbeliferae), mass of seeds with endosperm varied 15.8—fold among 2—yr—old plants that were grown from seedlings under similar conditions. Within individual plants, seed masses varied 2.6—fold to 8.1—fold. Forty—four percent of the variance was among seeds within umbels, 16% was between umbels within plants, and 40% was between plants. Plants varied in mean seeds mass from 3.7 to 8.3 mg, a 2.2—fold variation in means. The distribution of means around the grand mean was not skewed but was significantly leptokurtic. Coefficients of variation among the means averaged 26% (range: 16—48). These results together with the few other studies from natural populations in which large numbers of seeds have been weighed individually show much more variability in individual seed masses than is indicated by the common ecological impression (based mostly on comparison of means) that seed masses tend to be fairly constant.