[en] Sterols are essential insect nutrients, involved in some key metabolic pathways. Insects cannot synthesize sterols and must instead draw them from food. For bees, pollen is the only source of sterols, mainly provided in structures with 28 or 29 carbons (i.e., phytosterols). Phytosterol composition of pollen is highly variable among plant species, challenging the physiology and survival of generalist bees. Previous studies have shown that the honey bee (Apis mellifera) is able to handle this variability by adding endogenous sterols to provide a suitable diet to larvae. Such behaviour has never been investigated in other bee species, although it is a key element for understanding bee conservation and evolution. Here, we assessed the sterolic compositions of pollen loads from A. mellifera and compared them to those from generalist (i.e., Bombus terrestris) and wild specialist bee species, as well as to floral pollen. A total of seven plant species from six families and their associated visitors were considered. these results show that some species are able to modify sterol composition of pollen. In some case this modification consist in addition of a peculiar sterol. Moreover this study opens the way to new insights in bee origin and the evolution of their interactions with flowering plants.
