Taxonomic and functional diversity of urban bees of the world

Bees play a pivotal role in terrestrial environments. Urbanization can affect these organisms and the ecosystem services they provide. However, knowledge of the global diversity of urban bees is limited. Thus, we summarized data on urban bee species identities and occurrences; compared distributions of all bees with those found in urban environments; described traits and resource collection across latitudinal regions; and determined species' conservation status. We identified 1981 urban bee species, representing 9.5% of overall diversity. Nontropical regions had more studies and higher bee richness than tropical regions, indicating geographical bias. Family distributions of urban bees were similar to those observed for overall bee diversity. The Apidae family accounted for 35.1% of urban species worldwide. In the tropics, Apidae accounted for 69.0%. Most urban bees of the world were solitary (49.8%) and social (33.8%) (eusocial, 4.7%; kleptoparasite, 11%), were medium (41.8%) to small sized (36.2%), nested in soil rather than cavities (65.0%), and had the capacity to perform buzz pollination (65.0%). Only a small proportion of bees collected specialized resources (oil, 3.2%; resin, 12.1%; fragrance, 2.9%) and plant material (10.7%). Due to the dominance of Apidae, this situation differed in the tropics, where there was a higher degree of social (42.9%) and eusocial habits (20.1%), more large-sized species (42.9%), more cavity-nesting species (62.7%), and especially a higher representation of specialized resource collection, including oil (10.7%), resin (44.2%), and fragrance (17.6%). Most species (96.4%) had not had their conservation status evaluated. Our results showed that urban environments worldwide can support a high taxonomic and functional diversity of bees, but that this capacity differed across latitudes. Our findings can be used to inform management strategies that promote suitable nesting sites and provide specific resources for bees in each global region, making cities more bee friendly and maintaining the ecosystem services bees provide.