Pollinators are vital for the maintenance of ecosystem biodiversity and function. However, climate change has the potential to alter plant-pollinator interactions by influencing flower traits important for attracting pollinators. To anticipate the effect of climate change on plant-pollinator interactions, we examined how carbon dioxide fertilization and drought influenced floral display, floral volatile organic compounds (VOCs), and pollinator community composition and visitation rates in three native forb species and one invasive forb species in Southwest Montana. Plants were subjected to drought and double the current ambient atmospheric concentration of carbon dioxide treatments in a factorial design in growth chambers to simulate future climate scenarios. Traits important for pollinator attraction, including floral display and floral volatile emission, were measured, and pollinator visitation to these plants was observed in a field setting.
Results from our experiment demonstrate that flower traits and pollinator communities display species-specific responses to climate treatments. In one plant species, carbon dioxide enrichment increased floral display by 33.0%, increased VOCs emission rate by 42.1%, and changed the composition of VOCs. Experimental drought decreased flower size between 17.9-37.9% in all species. However, drought increased VOCs emission rates by 24.3-49.6%, and altered VOCs composition in two species. Pollinator communities responded to changes in plant attractive traits in all three native forbs, but not in the invasive forb species. Visitation rates of pollinators to the invasive forb remained two times greater across treatments than all other native forbs. Additionally, pollinator community composition was most consistent between treatments in the invasive forb compared to all three native forbs. These results highlight that the response of plants and pollinators to climate change are species-specific, with complex implications for plant-pollinator interactions. If these patterns hold for other communities of native and non-native plants, pollinators could maintain preferences for non-native plants in warmer, drier, and carbon dioxide enriched conditions.