PS 48-232 - Analysis of Hairy Versus Non-Hairy Bees Across an Urban Gradient

Abstract: Urbanization is thought to have a negative effect on the wild bee community possibly due to the reduction of habitat and foraging resources. However, some studies suggest that the genus Bombus is successful in urban settings. For example, our previous work has demonstrated a positive correlation between Bombus abundance and proxies of urbanization. Still, it is unclear what traits underlie the unexpected distribution of Bombus toward an urban landscape. One dominant morphological feature of Bombus is their hairiness, which might convey some adaptability to the urban environment. Hairy bees may be insulated against temperature swings, and exposure to pesticides or may have other unknown beneficial features. The present study investigates whether other hairy genera share Bombus’ tolerance of an urban habitat, which would suggest that hairiness contributes to the distribution of those bees towards urban areas. We examined bee abundance as it relates to hairy vs. non-hairy bees across an urban gradient using forest area, forest fragmentation, and impervious area as proxies of urbanization at six sites in Southeastern Massachusetts. Bees were collected bi-weekly using pan traps and sweep nets from early spring to late fall from 2016-2021.





Overall bee abundance was correlated with imperviousness (p< 0.05). However, hairy, and non-hairy bees did not differ in their relationship with imperviousness. The analysis of hairy bees alone showed a significant effect between forest cover and hairy bee abundance (p< 0.05). Bombus has a negative correlation with forest cover (R²=0.537) which differed from other hairy bees (R²=0.013; p< 0.05). The comparison of Bombus to Xylocopa, another large hairy genus, showed a significant effect of all three proxies of urbanization on bee abundance (p< 0.05). There was no difference between Bombus and Xylocopa’s relationship with imperviousness. Both Xylocopa (R²=0.173) and Bombus (R²=0.537) were negatively correlated to forest area, but with significantly different slopes (p< 0.05). Similarly, Xylocopa (R²=0.100) and Bombus (R²=0.343) showed different positive correlations with the fragmentation index. These data do not suggest a correlation between hairiness and bee abundance across an urban gradient. However, Bombus seems to behave differently than other hairy bees with the possible exception of Xylocopa, which shows similar trends.