Submitted to: International Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2005
Publication Date: 2/1/2006
Citation: Brunet, J., Sweet, H.R. 2006. The maintenance of selfing in a population of the Rocky Mountain Columbine. International Journal of Plant Science. 167:213-219.
Interpretive Summary: How much genes move via pollen partly depends on how much a plant can self-fertilize. Selfing means that pollen from one plant fertilizes ovules on that same plant. With selfing, pollen does not move from one plant to the next hence there is no gene flow via pollen. Selfing can occur when pollinators move pollen from one flower to the next on the same plant. This type of selfing is called among flower selfing. When among flower selfing is present pollen that would otherwise be available to go on other plants in the population (outcrossing) is lost to selfing. Moreover with among flower selfing pollinators move pollen from flower to flower just as they would for outcrossing hence more pollen is actually lost to selfing than if selfing occurred within a flower. When selfing occurs among flowers on the same plant one expects high selfing rate to be associated with low gene flow as significant amount of pollen is expected to be lost to selfing. When among flower selfing occurs one can no longer assume that selfing rate does not impact gene flow. Measuring the contribution of among flower selfing on a plant can help predict the potential for gene flow relative to an outcrossing plant. In this study we measure the contribution of among flower selfing to the selfing rate in the rocky mountain columbine. We estimated that 50 % of seeds resulted from selfing in the population and that selfing was mostly from among flower selfing. These data suggest that gene flow in this population is greatly reduced relative to a population with higher outcrossing rate. In insect-pollinated crops quantifying modes of selfing contributes to a measure of risk assessment for gene escape via pollen.
Technical Abstract: Pollination biology plays a major role in the evolution of selfing and the maintenance of mixed mating systems. We examine whether selfing in a population of A. coerulea is selected for or whether it is merely a non-adaptive consequence of adaptations for cross-pollination in a self-compatible plant with more than one flower open simultaneously. The comparison of selfing rate between groups of emasculated and control flowers on experimental plants helped quantify the contribution of geitonogamous and autogamous selfing to the selfing rate. While an increased seed set in control flowers suggested reproductive assurance, the genotypic data indicated that geitonogamous selfing made up the majority of the selfing and that autogamous selfing was negligible in the population. We examined whether bumble bees, the major pollinator in the population that year, visited control and emasculated flowers equally frequently. We quantified the impact of emasculated flowers on the level of geitonogamous selfing in control flowers. After examining the reasons behind the discrepancy between our seed set and genotypic data we concluded that selfing in A. coerulea is a non-adaptive consequence of adaptations for cross-pollination in a plant with large floral displays.