The Effect of Land Use Gradient on Adult Body Size of Bees in Eastern Tennessee

With the intensification of agricultural practices, bee habitats are undergoing changes, impacting the nutritional quality of resources available to bee larvae and leading to variation in adult body sizes. Because larger bee species can forage at greater distances from their nests, we predicted that intraspecific body size would respond differently to agricultural land use gradient depending on bee size at the species level. Our study emphasizes the effect of a varying agricultural land use gradient on adult body sizes of bees. Our experiment took place in East Tennessee where we established twenty plots each containing 18 native plant species, at five sites of varying agricultural land-uses, ranging from 6-48% agriculture. During the summer, using an insect vacuum, we collected 11,183 insects representing 99 bee species interacting with these native plants. We then haphazardly selected adult bees from 13 species that were found at all sites to measure their body size via intertegular distance (ITD). We found that the intraspecific adult body size of larger bees, such as Bombus impatiens, increased along with agricultural land use in the surrounding landscape. The body size of small and medium sized bee species did not change along the agricultural land use gradient. This indicates that agricultural land use affects bee species differently. Larger bees are able to forage at greater distances from their nests and carry more provisions, which might make them more resilient to agricultural land use. Smaller bees may be less resilient because they cannot forage as far. This is critical to consider for future landscape management practices to best ensure the pollination of crops. KEYWORDS: Pollinator Health; Wild Bees; Agriculture; Conservation; Spatial Ecology; Social Bees; Intertegular Distance; Land Use Change