The perils of forcing a generalist to be a specialist: lack of dietary essential amino acids impacts honey bee pollen foraging and colony growth

Commercial honey bee colonies pollinate large monocultures, which contain one type of food and thus, one unbalanced source of nutrients. We examined how a lack of dietary essential amino acids (EAAs) affects honey bee foraging behavior and colony growth. Using pollen traps and semi-synthetic diets, we raised bees on three treatments in the field: no diet manipulation, a diet with all 10/10 honey bee EAAs, or a diet with only 6/10 EAAs. In 2016, during a drought, bees raised on the diet lacking EAAs collected more pollen than bees raised with all EAAs, suggesting compensatory foraging. This was not found in 2017, when natural resources were likely more abundant. As such, honey bees lacking EAAs worked harder to fill the gap in the nutrient poor environment. In 2017, colonies raised on all 10 EAAs expanded slower than control colonies, and colonies raised on 6/10 EAAs did not expand at all. This suggests that EAA diversity, and likely other nutrients found in pollen, are essential for colony growth. Forcing this generalist pollinator to be a specialist drastically reduces colony growth and likely, honey bee fitness.