No wild bees? Don't worry! Non-bee flower visitors are still hard at work: The edge effect, landscape, and local characteristics determine taxonomic and functional diversity in apple orchards

Abstract

Native pollinators are key to enhancing fruit production in apple orchards and maintaining yield stability through taxonomic and functional diversity. Some studies suggest that the distance to the nearest native forest patch, the edge effect, or apple orchard management, modulate the richness and abundance of pollinators. However, such studies have focused on bees, thereby generating knowledge gaps about non-bee pollinators. This study looks at the taxonomic and functional diversity in central Chile, as well as the abundance of major pollinator groups (native beetles, flies, wild bees, and lepidopterans), and how these are influenced by landscape and apple orchard characteristics. For two seasons, native and managed pollinators were recorded in nine apple orchards with different management approaches (organic vs conventional) and apple varieties (Gala vs Fuji). The taxonomic and functional diversity of major pollinator groups were correlated with distance to the nearest native forest patch. We measured the edge effect on pollinators toward the interior of apple orchards and analyzed the results with one-way ANOVA. Lastly, we associated the diversity and abundance of pollinators with landscape and apple orchards characteristics using GLMM. Excepted managed bees and contrary to the global trend in apple studies, native flies and beetles were the most dominant pollinators, the latter being more abundant at the orchard edge. The distance to the native forest patch was correlated negatively to the functional richness and positively to body temperature, while that same variable influenced the abundance of total native pollinators, beetles, flies, and wild bees. The gala variety was found to attract greater pollinator richness and more wild bees, whereas organic orchards positively influence native flies and conventional orchards attract lepidopterans. Moreover, the number of honey bees influences the abundance of wild bees and lepidopterans. Land intensification practices could decrease the taxonomic and functional diversity of pollinators. Management alternatives like increased landscape heterogeneity or native habitat restoration, could to maintain apple fruit production in space and time.