Macronutrient composition in pollen affects development and survival in wild bees

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) from artificial nest substrates and reared them on diets
formulated with black poplar (Populus nigra) and dandelion (Taraxacum
officinale) 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.