Interacting effects of landscape and management on plant-solitary bee networks in olive orchards

Understanding how multi-scale environmental heterogeneity shapes the structure and functions of animal and plant communities is pivotal in agroecology. Our capacity to ensure the provision of ecosystem services (ES), the sustainability of agroecosystems and the efficiency of agri-environmental schemes (AES) relies on this knowledge. There is growing interest in how biodiversity and ES are affected by the interplay between landscape characteristics and agricultural management (e.g., intermediate landscape complexity hypothesis; ILCH). However, studies have typically focused on classical measures of community structure (e.g., species abundance, richness and biodiversity), tending to neglect the effects on the structure and stability of ecological networks and the increased risk of biotic homogenization (i.e., loss of beta-diversity). In this work, we use bee trap nests to sample pollen-solitary bee mutualistic networks in 9 pairs of olive groves under different management regimes (conventional vs. organic) in a landscape complexity gradient in southern Spain. We analyse the mutualistic networks at farm level to test the ILCH and study how agricultural practices and landscape complexity interact to affect the properties of these networks. We also explore the effects on spatial biotic homogenization by performing multivariate analyses of the composition and abundance of bee-plant communities and their pairwise interactions. The results show that solitary bee-plant networks have greater complexity and stability on organic olive farms embedded in relatively heterogeneous landscapes. Differences from conventional management were higher in landscapes of intermediate complexity but were non-significant on olive farms located in simpler landscapes. beta-diversity of bees, plants and their pairwise interactions was also greater on organic olive farms. In conclusion, human-induced environmental heterogeneity interacts at different scales to shape plant-solitary bee networks in olive groves, which may have important implications for ES provision and the effectiveness of agri-environmental measures. A free Plain Language Summary can be found within the Supporting Information of this article.