Investigating native bees in roadside habitats in the Southern Great Plains

Native bee populations are declining due to habitat loss and fragmentation, with roads contributing to habitat isolation. Roadside habitats, particularly rights-of-way (ROW), may offer refuge for pollinators, but their role in supporting bee communities is not well understood. To explore this, I investigated the relationship between road type, habitat characteristics, and pollinator communities along roadsides in Payne County, Oklahoma. I conducted 24-hour pan trap surveys assessing the richness and abundance of solitary native bees compared to road type, plant community characteristics, and vegetation cover. Road type had no significant effect on bee richness or abundance. However, habitat features, such as blooming forb richness, forb cover, and bare ground, were positively associated with higher bee abundance, while greater grass cover was linked to lower abundance. Greater litter cover was associated with increased bee richness, whereas flower abundance and forb cover were associated with lower richness. These findings highlight the importance of diverse and heterogeneous habitats for pollinators along roadsides. I also compared the abundance of live and dead large-bodied bees (Bombus spp.; Xylocopa virginica) along two-lane and four-lane undivided highways. Both dead and live bee abundance was significantly greater along two-lane highways. Increases in forb cover and flower abundance were associated with greater live and dead bee abundance. Additionally, adjacent land-use types influenced bee populations: non-bee-pollinated land was linked to greater live and dead bee abundance, while open water was associated with a reduction in live bee abundance. These results suggest roadside habitats play a complex role in supporting pollinators, with forb presence and flower availability being important. Finally, I examined the foraging behavior of two native bumblebee species, Bombus pensylvanicus and Bombus griseocollis, in roadside habitats. Both species collected pollen from multiple plant taxa, with B. griseocollis showing greater specialization. Floral preferences differed: B. pensylvanicus favored introduced plants, while B. griseocollis preferred natives. Additionally, body size and pollen load weight were significantly correlated for B. griseocollis, but not B. pensylvanicus, suggesting factors like time of capture or pollen grain size may influence pollen load weights. These findings underscore the importance of floral diversity in roadside habitats for supporting pollinator communities.