Floral abundance and corolla length predict the importance of species in connecting urban green areas

Despite the growing urbanization rate and its consequences on biodiversity and species interactions worldwide, the connection among urban green areas, performed by interacting species, is still poorly understood. We evaluated how plant and hummingbird species vary across the urban landscape of a tropical city in Brazil, identifying traits of species taking part in shared interactions between areas. We recorded plant-hummingbird interactions in five green spaces and two remnants of native vegetation, and: (1) contrasted species traits and species-level indices of both plants and hummingbirds; (2) evaluated how species and interactions vary among pairs of areas; (3) used a meta-network approach to identify which pairs of interacting species are more important in connecting areas. Species turnover was the component that better explained the beta-diversity of interactions among sites. In green spaces, plant species presented greater centrality and longer corollas than in remnants. However, both plants and hummingbirds were similarly specialized regardless of the type of area. Trees with large floral displays and with longer corollas shared more interactions and were present in more networks. Most interactions recorded in remnants are unique to them, due to the exclusiveness of some hummingbirds and plant species in such native habitat and are, thus, more sensitive to habitat conversion. Our findings support the importance of preserving remnants and using mass flowering native species in urban afforestation to maintain plant-hummingbird interactions and promote urban biodiversity. We evidenced that few interactions (16.6%) were redundant across areas, indicating a highly susceptible and fragmented system in the urban space.