One for all, all for one? Pollinator groups differ in diversity and specialization of interactions across urban green spaces

Urbanization poses significant threats to pollinators, but they may respond differently to habitat modification according to their nesting and foraging requirements. Despite the diversity of pollinator groups and species found in urban areas, research often focus on bees, neglecting other groups. Whether bee response to urbanization suffice in representing the wider pollinator spectrum, however, is poorly understood. Here, we examined how urbanization impacts the interaction networks between plants and different pollinator groups and evaluated the dissimilarities of urban green spaces at both local and regional scales within a Neotropical metropolis. Recording 1,404 interactions between 262 plant and 220 pollinator species, we found that network specialization varied among pollinator groups but was not affected by urban impervious surface cover. Such lack of difference may happen owing to the prevalence of generalist species across urban environments. Importantly, urban green spaces showed high dissimilarities in species and interactions, emphasizing the heterogeneity found across the urban landscape. Plant composition also varied between urban green spaces and was strongly correlated with interaction dissimilarities, indicating that floral resources contribute to unique interactions found in different areas. Our results suggest that although important, bees alone do not represent the wider response of pollinators to urbanization. Furthermore, the high dissimilarities influenced by site specific plant-pollinator co-occurrence underscore that multiple and connected green spaces are required to safeguard plant-pollinator interaction diversity and its vital ecosystem function in cities.