Autogamy and floral longevity in Mimulus guttatus

Floral longevity is an important determinant of reproductive success in Mimulus guttatus. We conducted a series of experiments investigating floral longevity in the Iron Mountain population of M. guttatus under controlled conditions. In the absence of pollinators, flowers typically last 4-6 d. However, this trait exhibits considerable plasticity. Reduced longevity is triggered by the successful deposition of pollen on the stigma but not by removal of pollen from the flower. Reducing water availability also reduced the duration of the floral life span. Experimental manipulations reveal that both male and female reproductive capacity declines continuously throughout the life span of a flower. This may indicate that flowers have obtained the maximum benefit possible by the time the corolla is abscised. We also performed manipulative experiments to determine when autogamy occurs in the lifetime of a flower. Although some autogamy occurs in the first couple of days postanthesis, most of it occurs late in the floral life span. Considering these results in relation to previous studies, we argue that the amount and timing of autogamy in M. guttatus flowers is likely to be determined by the level of pollinator activity in a population.