INTRAPOPULATIONAL VARIATION IN POLLEN-MEDIATED GENE FLOW IN PLANTAGO LANCEOLATA L

The extent of genetic variation in pollen-mediated gene flow distance was measured for a population of the wind-pollinated herb, Plantago lanceolata. Twenty-nine genotypes were collected from a natural population, clonally replicated, and grown to reproductive maturity in a greenhouse. Relative gene flow distances were measured for each replicate and genotype in a wind tunnel. Approximately five percent of the total variation in gene flow distance was attributable to variation among genotypes. Most of the remaining variation was attributable to differences between the early part of the growing season, when most of the flowering occurs, and the remainder of the season, when flowering is sparse. The rankings of the genotypes' gene flow distances showed significant concordance between the early-season measures and measures from later in the summer. There was no correlation between the average inflorescence height for a plant and the average gene flow distance for that plant. For analysis of pollen characteristics suspected as causal factors of variation in gene flow distance, the variation in gene flow distance was divided into two components: that due to environmental (seasonal) differences, and that due to the differences among genotypes within runs. Variation in both the buoyant properties of the pollen grains and their adhesiveness was significantly partially correlated with environmental variation in gene flow distance, while only the buoyant properties of the pollen grains were significantly partially correlated with among-genotype variation in gene flow distances.