Study area

We selected 18 oilseed rape fields across a large geographical area in Jiangxi Province, China (N28.35º–N28.99º, E115.26º–E115.82º). The mean distance between fields was 36.9 km (range: 5.8–75.2 km). As the maximum foraging range of most pollinator species is less than 2 km [28, 29], individual pollinators are unlikely to visit more than one field, and hence the pollinator communities in the study fields can be considered independent. The mean size of study fields was 845 ± 86 m² (range: 400–1400 m²) and all fields were sown between the middle and the end of October 2014 with the same traditional open-pollinated winter oilseed rape cultivar YangGuang-2009.