Reproductive patterns of solitary cavity-nesting bees responsive to both local and landscape factors

Understanding how local and landscape-level factors influence species abundances and distributions is crucial for conservation and restoration efforts. Effects of urbanization are often negative at a landscape level, but some taxa such as solitary cavity-nesting bees perform better in urban areas, due to increases in food, nesting, and habitat resources at the local level. In this study, we ask how local and landscape factors across an urbanization gradient influence three demographic aspects of reproduction for solitary-nesting bees: fecundity, brood survivorship, and total adults to emerge in the spring. In 2018–2019, we surveyed solitary cavity-nesting bees active in 18 grassland restoration sites across the city of Louisville, Kentucky, USA using constructed nest boxes. We found that bee larvae had increased survivorship in urban areas as compared to surrounding rural areas, possibly due to decreased nest parasitism. Additionally, we found bee fecundity to increase with the proportion of native flowers in the surrounding floral community. These results indicate that urbanization can benefit some groups of solitary bees when paired with local grassland restoration efforts. This highlights the importance of native plants and natural areas in the urban matrix to support pollinator communities.