PS 48-233 - The Effects of Urbanization on Wild Bees with Differing Functional Traits

Abstract: The essential role of bees in the ecosystem has raised concerns over their potential decline as urbanization increases and alters their habitats. Previous studies have investigated the effects of urbanization on the entire bee community, but few have focused on potential unique effects on individual genera. Some bees may be better fit to urban ecosystems compared to others due to differences in functional traits such as nesting guild. Some nesting guilds may have greater disadvantages than others if urbanization limits their habitat resources. To address this hypothesis, wild bees were sampled in southeastern Massachusetts bi-weekly from spring to fall in 2016-2021. Sampling was accomplished through pan traps and sweep netting at six different sites across a peri-urban to urban gradient. Proxies of urbanization were calculated using ArcGIS software. This study analyzed percent impervious surface and forest area within a 300-m radius as they relate to bee abundances of the top six genera, different nesting guilds, and the wild bee community as a whole.



Over six years 16,764 bees were sampled, identified to genus, and categorized by nesting guild. Nesting guilds differed in their relationships to imperviousness (p< 0.001). The abundance of wood nesting bees (Xylocopa) was not negatively correlated with imperviousness where all other nesting guilds were. This may suggest wood nesters have more nesting opportunities in urban habitats. The nesting guild most negatively correlated with imperviousness was parasitic. Spatial relationships were also investigated for our most abundant genera, all of which are ground nesting except Ceratina, which is stem nesting. Lasioglossum, Agapostemon, Halictus, Ceratina, and Augochlorella all had negative relationships with imperviousness, whereas Bombus abundance increased with imperviousness (homogeneity of slopes test p< 0.001). Similar to previous studies, this may indicate Bombus is better adapted to urban ecosystems. When investigating abundance relationships to forest cover we found differences among taxa (p< 0.001). Lasioglossum, Agapostemon, Halictus, and Augochlorella all correlated positively while Bombus and Ceratina correlated negatively. Overall, we found varying effects of urbanization on different nesting guilds, and among ground nesting genera. When studying the effects of urbanization, our results suggest advantages in scrutinizing genera and functional guilds rather than generalizing across the whole community.