Bumblebees are the most efficient pollinators of raspberry and strawberry in urban environments

Pollinators are essential for crop pollination, but pollinators differ in their pollination efficiency. In urban areas, environmental filters such as soil sealing or the urban heat island lead to biotic homogenisation of pollinator communities, with generalist species being favoured while specialist species are filtered out. Therefore, efficient pollinators may be excluded from urban areas. In the context of the development of urban agriculture, urban areas require pollination by efficient pollinators. Here, we ask whether pollinators sustained in urban environments are equally efficient, and whether urbanisation impacts the efficiency of pollinators delivering pollination services. Using strawberry and raspberry as experimental plants, we carried out single visit experiments over 2 years (2023 and 2024) in spring and autumn, to assess pollination efficiency in densely urbanised and suburban sites in the region of Paris (France). We measured fruit mass, malformation and seed set of fruits which developed from flowers having received a single visit from a pollinator. We found that bumblebees were more efficient than honeybees as pollinators of raspberry, but not strawberry, as measured by fruit mass. Bumblebees were also more efficient than small and large solitary bees for pollinating strawberry, and more efficient than large solitary bees for pollinating raspberry. These differences were detected on mass for strawberries, and on mass, seed set and fruit malformation for raspberries. Practical implication : Environmental filters in urban environments tend to favour few generalist pollinator species. On one hand, these environments support honeybees, which we found were not necessarily the most efficient. On the other hand, wild pollinators, in particular bumblebees, were more efficient than honeybees for pollination of strawberry and raspberry. Thus, urban conservation strategies should focus on promoting these wild and efficient pollinators by planting beneficial plant species in flower beds and providing nesting habitats for ground nesting pollinators. This would promote diverse and efficient pollinators and thus enhance pollination services for urban agriculture.