The impact of sunflower crop management on the conservation of foraging bumblebee (Bombus spp.) communities
A rapid decline of 33% of wild pollinating species since 1980 in the UK has meant management strategies within agroecosystems for conserving pollination services is increasing in importance. Recent interest has occurred in utilising mass flowering crops (MFCs), such as sunflowers (Helianthus), as a pollinator resource. However, research addressing specific pollinator communities within sunflower crop management and how these communities affect ecological functioning, are scarce. The present study investigates how sunflower crop management impacts bumblebee (Bombus) communities and their ecosystem services, thereby allowing the creation of effective, evidence-based management objectives. Foraging bumblebee communities were surveyed in the incrop and outcrop (2 m wide wildflower belt) of three sunflower fields at Rhossili, South Wales, and a control NNR site, Oxwich. Their ecosystem service role was evaluated through analysing functional trait diversity and individual-level variation using pre-selected bumblebee traits (tongue length, ITD mean measurements, foraging range, sex and flower visitation length). Bumblebee diversity was higher within the sunflower incrop than the wildflower outcrop (F(1,4) = 9.464, p = 0.022) and community composition differed between these habitats with species such as Bombus lapidarius and Bombus terrestris primarily foraging within the sunflowers. Yet, individual-level variation and all functional trait diversities, apart from sex, did not vary. These results suggest that MFCs do benefit wild bumblebee communities, likely due to the provision of additional large foraging resources, thus highlighting sunflowers’ potential within bumblebee conservation. The outcrop margin is still considered essential in encouraging agroecosystem resilience as it maintains board bumblebee community compositions and foraging opportunities when the crop is not flowering. However, the lack of variation in functional trait diversity across the habitats implies that management involving sunflowers may have little impact on the conservation of their ecosystem service role. This, alongside the possible potential for MFCs to compete with adjacent wildflowers and cause pollinator dilution, highlights that more research into pollinators’ functional diversity and MFCs’ limitations are needed before MFC is implemented as a pollination services conservation strategy.