From stream flows to pollination webs: Exploring the role of riparian environments in plant-pollinator interactions

The loss of natural habitats in agroecosystems is one of the major reasons for the decline in biodiversity. Riparian areas, which are known for their diverse flora and the many insects they support, are particularly vulnerable. Plant-pollinator networks are however far less studied in riparian areas than in other natural habitats such as grasslands, even though they could also be valuable for pollinator biodiversity conservation, especially in agroecosystems. By providing relay resources for pollinators that also visit crops such as rapeseed, riparian areas may also indirectly contribute to crop pollination services in agroecosystems. Based on field sampling, we built grassland and riparian plant-pollinator networks at five different sites in Northwestern France. We also sampled the visitors of rapeseed crops. First, we compared grasslands and riparian areas based on their plant and pollinator community composition and network metrics. Then, we investigated the drivers of pollinator abundance and richness found in these habitats. Finally, we evaluated indirect interactions between rapeseed and the wild flowers of riparian areas and grasslands through shared pollinators. Our results highlighted the interest of both riparian areas and grasslands in agroecosystems. The richness and structure of the networks were not different, and rapeseed pollinators benefited from the floral resources offered by both grasslands and riparian areas.