Reported declines in wild bees have led to concerns about the long-term survivability of these critical pollinators. Studies have suggested that human land use and urbanization negatively impact wild bees. However, the effect of urbanization on specific bee genera remains largely unknown. Anecdotal observations suggest that the genus Bombus (bumblebees) may be relatively resistant to urbanization compared to other bee genera. Bombus impatiens constitutes the majority of Bombus in Eastern United States. Their adaptability to a wide range of environments could suggest that Bombus impatiens may be particularly suited for urban settings. This study examines the effect of urbanization on Bombus compared to other wild bee genera, with specific focus on Bombus impatiens. Total non-Bombus genera, total Bombus, and Bombus impatiens abundances were examined for correlation with impervious land cover, forest area, and fragmentation. Bees were sampled biweekly via pan trap and sweep netting from early spring to late fall. Six study sites in Southeastern Massachusetts were analyzed with ArcGIS to calculate the percentage of impervious land cover, forest cover, and fragmentation (ratio of forest edge to forest area) as measures of urbanization.
Results/Conclusions
A total of 754 Bombus were collected from 2016-2019. 181 Bombus from 2018 were identified as either Bombus impatiens or other species of Bombus. No significant correlation was found between the percentage of impervious land cover and total Bombus abundance, while a significant negative correlation was found between total Bombus abundance and forest cover (R = -0.5493, p = 0.0054). In contrast, a significant positive correlation was found between non-Bombus and forest cover (R = 0.6663, p = 0.0004). Additionally, a strong positive correlation between total Bombus abundance and fragmentation was found (R = 0.4783, p = 0.018), while total non-Bombus abundance displayed a strong negative correlation with fragmentation (R = -0.8466, p= <0.0001). These results suggest that urbanization may impact Bombus differently than other genera. Analysis of Bombus impatiens alone did not suggest this species was notably different from the other Bombus species. In conclusion, increases in Bombus abundance seen with increasing forest area and fragmentation in an urban setting are opposite to changes seen in non-Bombus species of wild bees.