Effects of non-protein amino acids in nectar on bee survival and behaviour

Nectar mediates complex interactions that involve much more than simply food. Recent research has focused on nectar secondary compounds that appear to play a role in regulating interactions with other organisms. Secondary compounds may affect nectar feeders’ behaviour, interacting with their neurobiology. Here we focused on non-protein amino acids (NPAAs), which may constitute a large portion of floral nectar total amino acid content. They have long been known in floral nectar but their ecological function has not been investigated. We tested the effects of diets with low and high concentrations of γ-amino butyric acid (GABA) and β-alanine on the survival and behaviour of Bombus terrestris and Apis mellifera. We found that individuals of B. terrestris increased their walking activity when fed with solution containing a high concentration of β-alanine, and increased their flying activity when fed with the same solution containing a concentration of β-alanine similar to that occurring naturally in nectar. Bumble bees also showed a higher survival rate when fed with solution enriched with GABA, whether at low or high concentration. By contrast, honey bees were less sensitive to GABA and β-alanine in terms of survival and behavioural effects. These results demonstrate that NPAAs affect insect longevity and behaviour. The effects seem to be species-specific and to vary with concentration. Pollinator intake of NPAAs at concentrations occurring naturally in nectar may have ecological implications.