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The unique benefits of wild pollinators to the productivity of agricultural crops have become increasingly recognized in recent decades.
However, declines in populations of wild pollinator species, largely driven by the conversion of natural habitat to agricultural land and broad spectrum pesticide use often lead reductions in the provision of pollination services and crop production. With growing evidence that targeted pollinator conservation improves crop yield and/or quality, particularly for pollination specialist crops, efforts are increasing to substitute agriculturally intensive practices with those that alleviate some of the negative impacts of agriculture on pollinators and the pollination services they provide, in part through the provision of suitable pollinator habitat. Further, similarities between the responses of some pollinators and predators to habitat management suggest that efforts to conserve pollinators may also encourage predator densities. We evaluated the effects of one habitat management practice, the addition of cacao fruit husks to a monoculture cacao farm, on the provision of pollination services and the densities of two groups of entomophagous predators. We also evaluated the impacts of cacao fruit husk addition on pollen limitation, by crossing this habitat manipulation with pollen supplementation treatments.
The addition of cacao fruit husks increased the number of fruits per tree and along with hand pollination treatments, increased final yields indicating a promotion of the pollination ecosystem service provided by the specialist pollinators, midges. We also found that cacao fruit husk addition increased the densities of two predator groups, spiders and skinks. Further, the conservation of these predators did not inhibit pollination through pollinator capture or deterrence. The findings show that with moderate habitat management, both pollinator and predator conservation can be compatible goals within a highly specialized plant-pollinator system.
The effectiveness of this habitat manipulation may be attributable to the increased availability of alternative habitat and food resources for both pollinators and predators. The results exemplify a “win-win” relationship between agricultural production and biological conservation, whereby agricultural practices to support vital pollinators and pollination services can increase production as well as support species conservation.
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