Landscape context mediates the effect of pollinator garden enhancements on pollinator visitation and plant-pollinator interactions

Abstract Context Urbanization and associated habitat fragmentation and loss are leading factors contributing to the decline of pollinators, but may be ameliorated with gardens, green spaces, and other conservation efforts. However, there is limited research showing how pollinators respond to floral resource enhancements, and how landscape context mediates the conservation value of such enhancements. Objective Here we aimed to determine how plant diversity and landscape context mediate the value of pollinator gardens for insect pollinators across an urbanization gradient. Methods To do this, we selected 32 gardens varying in the amount of development in their surrounding landscapes, but all containing few plants attractive to native insect pollinators. We enhanced half of these gardens with a diverse mix of pollinator plants and examined insect pollinator responses both before and after enhancement across all gardens and over multiple seasons. Results Floral enhancements increased pollinator visitation rates to gardens in urban and suburban, but not rural, landscapes. Floral enhancements also increased the richness of unique plant-pollinator interactions, network modularity, and network diversity across all landscapes. Floral enhancements additionally changed the community composition of pollinators found in gardens in suburban and rural, but not urban, landscapes. Conclusions Enhancing gardens with diverse floral resources results in higher pollinator visitation rates and diversity of plant-pollinator interactions in more developed landscapes. Moreover, even when pollinator visitation rates were not increased (i.e., rural landscapes), enhancements increased network modularity and diversity. Thus, floral enhancements can improve the health and resilience of pollinator communities across landscapes.