Bees, butterflies, and other pollinators are vital for healthy ecosystems. They rely on floral nectar for energy, but it turns out that nectar is more than just sugar-rich aqueous solution. Studies have discovered that micro-components within the nectar, can significantly influence insects' flower preferences, impacting interactions between community plants and insects. 

In a species-rich alpine meadow in China, researchers from the Wuhan Botanical Garden of the Chinese Academy of Sciences investigated how nectar amino acids (AAs) influenced pollinator behavior. They analyzed the composition of 21 nectar AAs of 40 different plant species, and assessed its impact on the visitation frequency of over 200 insect species. 

Researchers found that while the nectar of most plants contained all 21 AAs, their relative composition varied significantly. Using Bayesian phylogenetically generalized mixed models, the team revealed that the presence of AAs, such as γ-aminobutyric acid (GABA) and methionine, significantly affected the visitation frequency of flower visitors. 

“We find that social bees, the dominant pollinators in the study meadow, are particularly drawn to nectar rich in GABA and methionine,” explains Porf. YANG Chunfeng.“We hypothesize that GABA may enhance cognitive functions, like memory and learning in these bees, making them more efficient foragers in Hymenoptera.”

The research also observed that these preferences varied across different types of flies within the Diptera order. Muscoid flies and meat flies favored nectar with high proline concentrations, while horseflies showed a negative response to arginine. These variations should be attributed to differences in the insects' feeding strategies and nutritional needs, demonstrating the complexity of plant-pollinator interactions.

The study emphasizes the significant role of nectar AAs in shaping the dynamics of plant-pollinator networks, providing new insights into the mechanisms of biodiversity maintenance. Those results have been published in Plant Ecology, titled "Quantitative analyses reveal interactions of community plants and insect flower visitors are associated with relative composition of nectar amino acids". It was supported by the National Natural Science Foundation of China.

The effect of different amino acids (AAs) in nectar on the visitation frequency of social bees (a), solitary bees (b), hoverflies (c), muscoid flies (d), meat flies (e), horseflies (f), Lepidoptera (g), Coleoptera (h). (Image by WBG)