Edge effects caused by roads impact many species but less is known about the impact of roads on native bees and wasps (Hymenoptera). To better understand effects of roadways on bees, we studied the diversity, abundance and community composition of native bees and wasps along county roads and adjacent forests within young (< 16 yrs) and mature aspen (> 32 yrs) (Populus spp.) stands in Wisconsin’s temperate Northwoods. From May – August 2015, we sampled five young and five older forest stands with pan traps along perpendicular transects from the roadway at set distances (0, 5, 10, 25, 50 m), and completed complementary detailed vegetation sampling.
We found the greatest overall abundance and diversity of bees and wasps were found closest to road edge, with lower abundances throughout the remaining transects. But this pattern differed with stand age, with a significant difference in the abundance of pollinators observed at road edge among the younger stands, while the older sites exhibited a near equal distribution throughout the transect intervals. These results suggest roadside habitats near younger forest stands provide important floral resources for native bees and wasps. We also noted seasonal variations in the abundance and diversity of pollinators with floral peaks, specifically in late June and early August. Future research will relate pollinator abundance, species richness and community composition patterns to fine-scale habitat features (i.e. floral abundance, woody debris availability and other stand characteristics).