The stingless bee Trigona fulviventris prefers sweet and salty over savory nectar

Abstract

Nectar, an important reward in plant-pollinator interactions, mainly provides sugars, but also other nutrients. Nectar sugar content is known to affect pollinator preferences, while the effect of other nectar nutrients on flower visitor choices is less well understood. To explore whether nectar nutrients affect the foraging preferences of the stingless bee Trigona fulviventris, we conducted feeding choice experiments with sucrose solution enriched with either an amino acid mixture (in high and low concentrations), sodium chloride (table salt), a fatty acid mixture, or quinine (a bitter tasting substance used as negative control) against pure sucrose solution in a lowland rainforest in Costa Rica. Bees were first trained to feeders presenting either a yellow (only sucrose solution) or a blue (sucrose solution plus tested substance) visual cue that the bees could use to associate with the solution content. They were subsequently offered a choice between the blue and yellow feeders in an unrewarded test. The bees preferred pure sucrose solutions over sucrose solutions with quinine, amino acids, or fatty acids, but not over solutions with salt. Our findings indicate that T. fulviventris is able to differentiate various nutrients in nectar and prefers pure sucrose solution or sucrose solutions with salt. Sugar and salt may therefore represent important nutrients in nectar and are likely key cues to assess nectar quality in tropical stingless bees. In contrast, other nutrients appear to compromise the bees’ taste for nectar and are likely obtained from other sources.