Wild bees enhance honey bees’ pollination of hybrid sunflower

Abstract

Pollinators are required for producing 15-30% of the human food supply, and farmers rely on managed honey bees throughout the world to provide these services. Yet honey bees are not always the most efficient pollinators of all crops and are declining in various parts of the world. Crop pollination shortages are becoming increasingly common. We found that behavioral interactions between wild and honey bees increase the pollination efficiency of honey bees on hybrid sunflower up to 5-fold, effectively doubling honey bee pollination services on the average field. These indirect contributions caused by interspecific interactions between wild and honey bees were more than five times more important than the contributions wild bees make to sunflower pollination directly. Both proximity to natural habitat and crop planting practices were significantly correlated with pollination services provided directly and indirectly by wild bees. Our results suggest that conserving wild habitat at the landscape scale and altering selected farm management techniques could increase hybrid sunflower production. These findings also demonstrate the economic importance of interspecific interactions for ecosystem services and suggest that protecting wild bee populations can help buffer the human food supply from honey bee shortages.agriculture ͉ biodiversity ͉ conservation ͉ ecosystem services ͉ Helianthus annuus T he honey bee (Apis mellifera) is the principal species used for crop pollination worldwide (1); the pollination services honey bees provided to U.S. crops were worth $14.6 billion in 2000 (2). Although honey bees pollinate a wide variety of crops, they are often relatively ineffective pollinators on a per-visit basis (1,(3)(4)(5)(6). Farmers obtain adequate pollination services by bringing large numbers of honey bees to crop fields. However, supplies of honey bees have declined, in part because of problems caused by parasitic mites and pesticide misuse. Since the 1970s the number of managed honey bee colonies in the U.S. decreased from Ͼ4 million to 2.41 million; declines were also reported in Europe (5,(7)(8)(9)(10)(11)(12)(13)(14). Several documented examples show that reductions in bee abundance can cause reduced crop yields (15, 16). If crop production suffers from diminished supplies of honey bees now or in the future, then an increase in the per-visit pollination efficiency of honey bee individuals may be immensely valuable for global food production.Non-Apis bees, also known as pollen bees (hereafter wild bees), are also valuable for crop pollination (17), but far less is known about their ecology and contribution to crop production. Previous studies have indicated that surrounding and in-field habitat affects the composition of wild bee communities that pollinate crops (18)(19)(20)(21)(22)(23)(24)(25). Both the abundance and diversity of wild bee communities are associated with increased crop pollination (16,21,22), and in some cases wild bee diversity predicts crop production better than wild bee abundance (20). Species...

Honey bee visitation to sunflower: effects on pollination and plant genotype

“…Moreover, the combination of A. mellifera and other bee species results in improvement of pollination in sunflower hybrids (DeGrandi-Hoffman and Watkins, 2000). Interactions between wild and honey bees increased five times the bee's efficiency pollination in sunflower hybrid (Greenleaf and Kremen, 2006). The same authors commented that indirect participations caused by interactions among bees species were five times most important than direct contributions of wild bees in sunflower pollination.…”

Red mason bees cannot compete with honey bees for floral resources in a cage experiment

“…Greenleaf and Kremen (2006) observed interactions between wild bees and honey bees in which wild bees displaced honey bees from flowers. We also found that males of the red mason bee displace honey bees more often than vice versa, with male mason bees displacing intraspecific males and females as often as honey bees.…”

Pollination service delivery for European crops: Challenges and opportunities

“…Although the extent to which 245 manage honey bees are competing with native bees is debatable, some studies have shown that 246 competition takes place with bumblebees for access to nectar (Thomson, 2004). For example, the 247 interaction between wild and honey bees contributes more than the direct contribution of the 248 commercial bees to the sunflower pollination (Greenleaf et al, 2006). These findings demonstrate 249 the economic importance of interspecific interactions for ecosystem services and suggest that the 250 protection of wild bee pollinators can help a lot the food production supply by compensating the 251 commercial bees' scarcity (Greenleaf et al, 2006).…”

“…For example, the 247 interaction between wild and honey bees contributes more than the direct contribution of the 248 commercial bees to the sunflower pollination (Greenleaf et al, 2006). These findings demonstrate 249 the economic importance of interspecific interactions for ecosystem services and suggest that the 250 protection of wild bee pollinators can help a lot the food production supply by compensating the 251 commercial bees' scarcity (Greenleaf et al, 2006). This can promote variation in the pollination 252 service delivery that is difficult to take into account in the model.…”