Woody habitats promote pollinators and complexity of plant–pollinator interactions in homegardens located in rice terraces of the Philippine Cordilleras

Abstract

Bees are important pollinators of wild plants and crops, but little is known about bee habitat requirements and pollinator management in tropical mountainous agricultural regions. Here, smallholder farmers produce fruits and vegetables in homegardens that depend upon or benefit from bee pollination. We hypothesized that abundance and richness of wild and domesticated bees and the complexity of plant–pollinator interactions are higher in homegardens surrounded by woody habitats than in homegardens found farther from woodlands. Bees were sampled in 20 homegardens in the rice terraces of the Philippine Cordilleras. We used linear mixed effect models to analyse effects of woody habitats around homegardens on bee richness and abundance. Based on pooled observations for each garden category, we built pollinator–plant interactions networks to illustrate shifts in interaction frequencies. We recorded 354 bee individuals of 13 wild and one domesticated bee species (Apis cerana). Wild bee richness was significantly higher in homegardens surrounded by woody habitats. Bee abundance increased significantly with increasing flower cover. Wild bees visited cultivated plants significantly more often than domesticated bees. Six vegetable species and 76% of all flower visits on cultivated plants in total were performed by wild bees and three plant species and 24% by domesticated bees. Pollinator–plant networks were more complex in homegardens surrounded by woody habitats. We conclude that woody habitats increase abundance and richness of wild and domesticated bees. Increasing availability of floral resources also promotes bee abundance. In order to promote pollination services in the landscape mosaic of smallholder rice farms, woody habitats and forest fragments together with numerous floral resources should be protected and restored.