Manipulation of Floral Symmetry Does Not Affect Seed Production in Impatiens Pallida

The outcomes of past research concerning the role of floral symmetry in plant-pollinator interactions are mixed. Field manipulations of plants, as well as experiments using artificial arrays, have found evidence for and against a direct relationship between the degree of floral symmetry and subsequent reproductive success. In this study, we test the hypothesis that deviations from perfect floral symmetry in Impatiens pallida (Balsaminaceae) result in direct fitness costs. In two field seasons, we manipulated experimentally floral symmetry in separate populations of plants and measured seed set. We did not address any possible effects of floral asymmetry on male function. We found no significant differences in seed number per fruit among control, symmetrically cut (30% on both lobes), asymmetrically cut (60% on left lobe), and severely mutilated (100% on left lobe) flowers in the field. Post hoc power analyses show that a prohibitively large sample size would be required to detect the observed differences in seed set among treatments. Moreover, the magnitude of the observed differences among treatments is biologically irrelevant. We conclude that the degree of floral symmetry does not affect female reproductive success in this system.