Plant-pollinator interactions and bee functional diversity are driven by agroforests in rice-dominated landscapes

Abstract

Wild and domestic bees are essential for the pollination of crops in home gardens, agroforests and vegetable fields of rice smallholders. However, it remains unclear how rice fields and agroforests affect pollinator communities. We investigated the effects of habitat loss and isolation on four different components of bee diversity: abundance, species richness, functional diversity, and plant-pollinator interactions.Flower-visiting bees were recorded in a lowland rice-based production region on the Philippines. We sampled two different land use systems (agroforests and rice fields) and along a gradient of habitat isolation (isolated rice fields and rice fields connected to agroforests).All components of bee diversity were higher in agroforests than in rice fields. Especially above-ground nesting and long-tongued species were adversely affected by rice field habitats and body sizes decreased with isolation from agroforests. For plant-pollinator interactions we found that plants received less diverse pollinator visits in isolated rice fields.In conclusion, agroforests provide important food and nesting resources for bees that translate into taxonomically and functionally diverse pollinator communities as well as stable pollinator visitation networks. These cultivation systems should therefore be maintained or expanded to ensure pollination services and biodiversity conservation. On the contrary, rice fields provide habitat for only few generalist bee species and flower visitation is reduced in isolated rice fields, possibly also leading to impaired pollination of wild plants and crops. Connectivity between bee habitats located in rice production areas is probably disrupted even after a few hundred meters and should therefore be promoted by measures like flower strips in rice fields.