The Maintenance of Selfing in a Population of the Rocky Mountain Columbine

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 Aquilegia coerulea is selected for or whether it is merely a nonadaptive 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 contributions of geitonogamous and autogamous selfing to the overall selfing rate. While an increased seed set in control flowers indicated 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 bumblebees, the major pollinator in the population that year, visited control and emasculated flowers with equal frequency. We quantified the impact of emasculated flowers on the level of geitonogamous selfing in control flowers. After examining the reasons behind the discrepancy between seed set and genotypic data, we concluded that selfing in A. coerulea is a nonadaptive consequence of adaptations for cross-pollination in a plant with large floral displays.