Macronutrient composition in pollen affects development and survival in wild bees

Abstract Pollinators rely on diverse floral resources to meet their nutritional needs, as pollen macronutrient composition varies significantly among plant species, influencing bee development and survival. In this study, we collected freshly laid eggs of the small carpenter bee ( Ceratina calcarata ) (Hymenoptera: Apidae) Robertson, 1900 from artificial nest substrates and reared them on diets formulated with black poplar ( Populus nigra ) (Malpighiales: Salicaceae) Linnaeus, 1753 and dandelion ( Taraxacum officinale ) (Asterales: Asteraceae) F.H. Wigg, 1780 pollen, while closely monitoring developmental metrics, lipid content and survival. We also conducted macronutrient analyses on both pollen types to quantify protein, amino acids, fatty acids and sugars. While dandelion pollen is abundant and carbohydrate‐rich, it contained lower levels of protein, essential amino acids and several fatty acids in our analyses, a nutrient profile that corresponded with slower larval development in our study. In contrast, black poplar pollen, despite being primarily wind‐dispersed, had higher concentrations of protein, essential amino acids and fatty acids in our analyses and supported better developmental performance. Bees reared on black poplar pollen exhibited faster maturation, larger head widths and greater body mass, highlighting the possible role of protein availability in development. Survival analysis further revealed that protein‐rich diets supported higher brood viability, whereas bees fed dandelion pollen experienced delayed development and reduced body sizes. Bees on 50:50 mixed diets displayed intermediate development times and improved survival, highlighting the benefits of dietary diversity in mitigating nutritional stress. These findings emphasize the importance of arboreal pollen as a possible nutritional resource and the potential to incorporate tree pollen sources into conservation planning. Given the increasing pressures of habitat loss and climate change, ensuring access to nutritionally diverse pollen sources may be useful for sustaining pollinator populations and promoting ecosystem resilience.