Impact of pollen nutritional composition on Bombus impatiens health

Pollen provides bumble bees with protein, lipids, vitamins, and minerals, while nectar serves as a source of carbohydrates. Due to the diversity of nutritional content present in pollen, wild bees must to forage for their specific dietary needs. Unfortunately, climate change and changing landscape composition continue to reduce the consistency, distribution and abundance of these critical resources. A consensus is emerging that nutritional requirements of bees can vary significantly by species. Bombus impatiens, an important and prolific pollinator, prefers high protein pollen. Current research has highlighted the health impacts of sub-optimal nutrition on bumble bee colonies; however, these studies have relied on artificial diets that do not fully replicate natural field conditions. We collected honey bee pollen from multiple locations through 2023 and 2024, and quantified the protein and lipid concentration of each sample. We then started microcolonies of Bombus impatiens consisting of three workers and tracked their development over six weeks. Microcolony offspring were weighed and frozen at -80°C to be assessed for characteristic markers of developmental stress, such as developmental asymmetry. Our results suggest that not only do higher protein diets improve offspring production, but they also lead to larger and healthier offspring. Conversely, low-protein diets delayed offspring production and reduced offspring size. This research highlights the importance of high protein pollen in supporting healthy bumble bee offspring development and provides valuable insights to guide future research and restoration efforts aimed at improving bumble bee nutritional resources.