Differential functional group response to environmental change alters plant-pollinator interactions in a prairie system

Changes in atmospheric CO₂ concentrations are expected to influence plant allocation to reproduction and to floral attractive traits and, therefore, should influence pollination success. However, the effects of CO₂ on mutualistic interactions between plants and pollinators have been virtually ignored. To explore these interactions, we experimentally elevated CO₂ and quantified the floral traits and pollination success of eight prairie forbs, including four legumes: Amorpha canescens, Lespedeza capitata, Lupinus perennis and Petalostemum villosum; and four non-N₂-fixing forbs: Achillea millefolium, Anemone cylindrica, Asclepias tuberose, and Solidago rigida. We evaluated inflorescence number, inflorescence size, display size, and height to inflorescence. We observed pollinators for twenty minutes intervals and recorded pollinator behavior, such as number and length of visits per inflorescence per plant, and calculated visitation rates. Legumes and non-N₂ fixing forbs responded differently to eCO₂ in the number of flowers produced per inflorescence, and pollinator behavior responded accordingly. Our results demonstrate that environmental change will influence relationships with plants and pollinators, and we suggest that the magnitude and direction of these effects on plants will depend on the specificity of the pollinator as well as the breeding system of the plant.