Seed Production and Insect Visitation Rates inHesperis matronalisAre Not Affected by Floral Symmetry

Abstract

In the past decade, field manipulation and pollinator choice experiments utilizing arrays of natural and artificial flowers have yielded mixed results with respect to whether symmetric flowers receive higher visitation rates or produce more seeds compared to asymmetric flowers. In this article, we test the hypothesis that deviations from perfect floral symmetry result in decreased seed production and reduced rates of insect visitation. We performed a floral manipulation experiment in two concurrent years with Hesperis matronalis (Brassicaceae) to investigate how seed production per fruit was linked to floral symmetry. In addition, we performed two replicated array experiments using model plants and flowers based on H. matronalis to investigate whether insects make decisions to visit plants on the basis of floral symmetry and whether insects use floral symmetry as a cue to discriminate among flowers within plants. We find no clear evidence that deviations from perfect floral symmetry affect insect visitation rates to plants or flowers within a plant and no clear association between floral symmetry and seed production. However, our array experiments suggest that insects use flower size as a primary cue to discriminate among plants but not among flowers within a plant.