The presence of generalist plants in urban greenspaces predicts pollinator diversity

Jacob S. Francis , Nadja Pernat, Adam Bloom, Antonia J. Millet, James J. Lange, Marina Marquis, Brittany M. Mason, Corey T. Callaghan 

Urban greenspaces are increasingly important for pollinator conservation, yet it remains unclear whether pollinator diversity is better predicted by overall plant richness or by the presence of particular plant species with central roles in the pollination network, referred to as hub species. Using community science observations from 39 urban greenspaces in Broward County, Florida, we constructed a regional plant-pollinator metanetwork and identified the five most highly connected plant species as interaction hubs. We then tested whether greenspaces containing more of these hub plants supported greater pollinator richness. Pollinator richness increased with hub plant richness, and this relationship was nonlinear, with evidence of diminishing returns as additional hub species accumulated. The observed hub set explained pollinator richness better than randomly assembled plant sets of equal size, indicating that the effect reflects the network roles of particular plant species rather than the presence of any common taxa. Our results suggest that plant identity and interaction role can outperform plant richness alone in predicting pollinator diversity in urban greenspaces. Regional metanetworks may therefore provide a practical framework for identifying plant species that disproportionately support biodiversity in fragmented urban landscapes.