D3481: The effects of urbanization intensity on bumblebee-plant network structure and floral resource topological roles

Terrestrial ecosystem functioning is reliant on animal pollinators to facilitate plant reproduction, though these pollination services faces threats due to declining pollinator populations. Bumblebees have become a focal taxon for understanding overall pollinator declines as they are the primary pollinators of many cultivated and wild plants. Studies indicate landscape homogenization has led to changes in bumblebee distribution, abundance, composition, and forage availability.

However, few studies have concurrently examined the extent to which urbanization intensity and concomitant changes in plant communities influence bumblebee composition and dietary breath. Our ongoing study examines bumblebee-plant networks across northern Illinois representing varying levels of urbanization intensity from 2022-2025. Bipartite networks and modularity analyses will assess community resilience to secondary extinctions and species’ importance within the network through network-level and species-level metrics.

Preliminary results identify associations between bumblebee biodiversity metrics and urbanization intensity, highlighting the influence of habitat quality. While bumblebees initially appear to be generalist pollinators and are likely resilient to landscape-scale changes, network analyses elucidate complex floral usage patterns. Bumblebee-plant networks demonstrate considerable variation in floral breadth among different bumblebee species. The composition of plants in low and high developed networks were significantly different, with urbanization intensity explaining 48% of the variation in diet. Connectance, robustness, and interaction evenness indices were lowest in high developed sites indicating a lack the interaction complexity of a stable community robust to perturbations. Modularity analysis assigned the following plant species topological roles: (low) Monarda fistulosa, Dalea purpurea, and Trifolium pratense, (medium) Silphium perfoliatum, and (high) Eutrochium purpureum.