Additive and interactive effects of pollination and biological pest control on crop yield

1. Insect pollination and biological pest control simultaneously influence crop yield, but are often investigated individually. This can lead to under- or over-estimation of the importance of individual services when they interact to affect yield. Recent, limited evidence from field studies showed contrasting results with both additive and non-additive positive and negative effects. 2. To disentangle the mechanisms underlying these responses, we conducted a greenhouse experiment and a field study. We tested the potential and realised contribution of insect pollination to cotton boll retention and yield under various pest pressures and biocontrol levels. 3. We found both additive and interactive effects of insect pollination and biocontrol within a single crop system depending on the level of pest pressure. In the greenhouse experiment, pollination did not contribute to cotton boll retention and final yield at low pest pressure. At high pest abundances boll retention and final yield were...