Wild bee abundance and diversity in an urban landscape: the importance of preserving native vegetation

Abstract

Urbanization is considered to be a major threat to biodiversity, habitat destruction and fragmentation hamper the establishment and dispersal of many species. Nevertheless, some species are resilient to urbanization. As important pollinators, wild bees provide an ecosystem service to natural, agricultural and urban ecosystems. It is not clear to what degree the urban environment can be a refuge for wild bees. We assessed changes in the abundance, species richness, and composition of wild bee community along an urbanization gradient in a semi-arid climate. Over two years and on a monthly basis, bees were sampled using colored pan traps at six sites with different degrees of urbanization. A total of 525 individual bees belonging to 15 species were trapped. The abundance and species richness of bees was positively correlated with native vegetation and negatively correlated with urbanization with soil-nesting species completely absent from highly urbanized sites. The amount of native vegetation was found to be the most important driver of wild bee species abundance and diversity. Our results suggest that the degree of urbanization is an important factor that can cause loss of pollinator diversity. Nonetheless, the incorporation of areas with native vegetation in urban planning has the potential to mitigate the negative effect of urbanization.