Effects of rare arable plants on flower-visiting wild bees in agricultural fields

Arable plants and wild bees are negatively affected by agricultural intensification, one of the major drivers of global biodiversity loss. However, it remains unclear how endangered and low competitive arable plants (rare arable plants) contribute to the persistence of flower-visiting wild bees by providing additional flower resources in agricultural landscapes. Thus, the effects of sowing 10 rare arable plant species on wild bees were investigated in an experimental field and on 10 different arable farms on nutrient-poor soils. Sowing of rare arable plants on cropped and uncropped plots was compared to annual and perennial wildflower strips. Results showed that rare arable plants on uncropped plots attracted as many wild bees as wildflower strips. Wild bee abundance and species richness increased in the autumn-sown crops in the second year, likely because winter annual rare arable plants were preferred. In particular, rare arable plants provided flowers preferred by long-tongued bumblebees, which are often lacking in intensively managed arable fields. Our study shows that sowing of rare arable plants can increase niche diversity and therefore resource availability for wild bees, and it can also conserve diversity of arable plants in degraded agricultural landscapes. Conservation of arable plants through sowing can also support wild bee communities and may become an important tool in pollinator-friendly management of arable land.