Effect of protein and lipids in pollen on the developmental success of the native solitary bee <i>Osmia lignaria</i> Say

The health of solitary bees is dependent on the pollen they consume, driving their development from larvae to pupae. Nutrients such as proteins and lipids play an important role in bee development and could be an important key in conservation efforts to support declining populations. We examined the concentration of protein, total lipids, and 13 individual lipid classes in pollen provisions collected from the native solitary nesting bee, <i>Osmia lignaria</i> Say, at 22 sites in urban and rural landscapes in western Washington over three years and during two distinct foraging periods. The results indicate that protein concentrations in pollen did not significantly affect larval development. We detected higher lipid concentrations in the second foraging period, which was also associated with increased larval developmental success. Using Next-Generation sequencing on collected pollen, we also ascertained the plant genera in pollen and observed that plant richness did not differ significantly between the two foraging periods even though levels of lipid concentrations did. Individual lipid classes may play a role in the successful development of <i>O. lignaria</i>, as hexosylceramide and cholesterol ester were positively associated with <i>O. lignaria</i> larval developmental success, which emphasizes the need for additional studies on the role of individual lipid classes on bee development.