Effect of flower strips on wild bees (Apiformes) and honeybees: Implications for the design of mixtures for pollinators

Honeybees are an important economic source for humans and fundamental pollinators for many crops worldwide. Still, interaction and overlap of trophic resources between honeybees and non-managed pollinators, such as wild bees, have been recently studied, and concerns about possible competition have been raised in environments where the number of hives is high. Actions that focus on supporting pollinators shall consider how to balance the presence of honeybees and wild pollinating species. In this work, we have investigated the effect of sown mixtures of entomophilous plants on wild bees and honeybees in a Mediterranean area. We demonstrated that sown plots dominated by one or a few flowering species affect the abundance of wild bees. We also found that when honeybees dominated (more than 50% of the observed specimens), plant-pollinator networks were more simplified and homogeneous than when wild species prevailed. These results show that sowing flower strips in small portions of arable surfaces, as encouraged by the European Common Agricultural Policies, or in urban and periurban areas, as a conservation practice for pollinators, requires careful consideration. In conclusion, sown nectariferous and/or polleniferous plants should develop into species-rich oligotrophic flowering areas to effectively support wild pollinators and reduce possible interspecific competition. • Floral, phenological and functional diversity support wild bee biodiversity. • Mass blooming grasslands by few plant species attract high density of honeybees. • Honeybees dominated plant-pollinator networks are more homogeneous and simpler. • Wild bees dominated plant-pollinator networks are more balanced and diverse. • Oligotrophic grassland lower competition between managed and non-managed bees.