Increasing wild bee richness and abundance on sequentially flowering cultivars of a pollinator-dependent crop

Many insects have a crucial role as pollinators in both natural ecosystems and agricultural systems. Reports of declining pollinator populations highlight the question how we can support them. Next to semi-natural habitat, different land use types can provide resources for pollinators. However, whether and how different cultivars of pollinator-dependent crops support pollinator populations has not been studied to date. This preliminary study investigated how the abundance of Osmia cornuta and the richness, abundance and community composition of wild pollinators (i.e. wild bees and hover flies) fluctuates throughout the bloom period of three sequentially flowering sweet cherry (Prunus avium) cultivars. Total pollinator richness and abundance increased throughout the bloom period of the different cherry cultivars. This increase was driven by an increase of wild bee richness and abundance, coupled with a decrease of nest-searching bees. The abundance of O. cornuta was found to in-crease throughout the bloom period. Furthermore, the composition of the pollinator community was significantly different across the different cultivars. Results of this preliminary study reflect the dynamics of wild bee emergence, mating and nest construction, which results in an increase in pollinator diversity and abundance in spring. This study also provides the first evidence that sequentially flowering cultivars of a pollinator-dependent crop can provide complementary floral resources that support complementary pollinator communities. Given the importance of wild pollinators for crop pollination, these results have implications for crop production and pollinator persistence in agricultural landscapes