Ecological determinants of interactions as key when planning pollinator-friendly urban greening: A plant-hummingbird network example

Urban green spaces may function as habitats for pollinators. However, it is poorly understood how distinct ecological drivers determine the interactions between pollinator and plants in urban communities, and how pollinator-friendly plants may be selected based on these determinants. Here, we describe an urban hummingbird-plant interaction network in Brazil and evaluate the ecological determinants of pairwise interactions (abundance, morphology, and phenology). Moreover, we used a modeling framework to simulate species removal from networks while allowing for rewiring of interactions, to contrast the importance of native and exotic plants for the network robustness. The studied network showed low specialization and modularity, with one short-billed hummingbird species, Glittering-throated Emerald (Chionomesa fimbriata), dominating the recorded interactions. Phenological overlap was the main determinant of pairwise interaction frequency between hummingbirds and plants. Because morphological matching did not impose strong constraints in the network, simulation models including rewiring based on morphology conferred high robustness after species removal. Furthermore, as exotic plants were only a minor component in the studied network, their removal did not greatly affect network robustness. Our findings demonstrate the importance of considering phenology when planning urban greening for conservation of pollinators. Additionally, we illustrate an analytical procedure that can be applied to quantitatively assess the importance of distinct species/groups for urban interaction networks.