Effects of Non-Protein Amino Acids in Nectar on Bee Survival and Behavior

Nectar mediates complex interactions between plants and animals. Recent research has focused on nectar secondary compounds that may play a role in regulating some of these interactions. These compounds may affect the behavior of nectar feeders by interacting with their neurobiology. Non-protein amino acids (NPAAs) can constitute a large portion of the amino acid content of floral nectar, but their ecological function has, to date, not been investigated. In this study, we tested the effects of diets with low and high concentrations of gamma-amino butyric acid (GABA) and beta-alanine on the survival and behavior of Bombus terrestris and Apis mellifera. The most apparent effect on longevity was observed for B. terrestris workers that fed on high concentration of GABA, with longevity increased. By contrast, neither of the two NPAAs (at either concentration) had an affect on A. mellifera longevity. At the low NPAA concentration, only B. terrestris workers showed a difference in consumption, consuming more beta-alanine solution than the other two solutions. By contrast, at the high NPAA concentration, only A. mellifera workers showed a difference in consumption, consuming more beta-alanine solution. The effects of the NPAAs on behavior differed between the two species, with B. terrestris appearing more sensitive to the NPAAs than A. mellifera. After consuming NPAAs, B. terrestris showed changes in three (walking, flying, stationary) of the four behaviors recorded, although the effects varied with concentration and compound. In contrast, honey bees only showed a change in feeding behavior, with consumption of both NPAAs (at low concentrations) resulting in a decrease. Thus, pollinator intake of NPAAs may have important behavioral/ecological implications.