The consequences of floral herbivory for pollinator service to Isomeris arborea

Flower-feeding insects may reduce the reproductive success of their host pl ant in subtle ways that go beyond a direct reduction in gametes. Pollinator s may respond to floral damage by visiting damaged plants at lower rates. F ewer visitations to the plant may result in fewer flowers that receive poll inator service and as a consequence lead to lower male and/or female reprod uctive success. In a two-year study, we examined the direct effect of flowe r predation by Meligethes rufimanus on the floral display of Isomeris arbor ea, and the indirect effect of herbivory on pollinator behavior. Plants exp osed to herbivore attack produced fewer functional inflorescences than plan ts protected from herbivory. Undamaged flowers produced three times as much nectar per flower as damaged flowers. Likewise, protected plants had over twice as many anthers per flower as exposed plants. Pollinators responded b y visiting damaged flowers less, and exposed plants had lower flower visita tion rates than protected plants. Pollinators also visited patches of prote cted plants more frequently than exposed patches. These results show that f loral herbivory reduces pollinator service and thus may reduce reproductive success indirectly, as well as through the direct consumption of viable ga metes.