Floral nectar contains diverse non-sugar secondary metabolites that can modulate pollinator behavior and physiology. Although individual compounds such as caffeine enhance memory in honey bees, pollinators naturally encounter multi-compound chemical environments whose combined effects remain unclear. Here, we tested whether two nectar constituents commonly present at trace concentrations-caffeine and arginine-modulate associative learning, long-term memory retention and short-term survival in the South American bumblebee Bombus pauloensis. Using a classical olfactory conditioning paradigm, each compound was administered alone or in combination at two ecologically realistic concentrations. Individually, both compounds enhanced acquisition and long-term memory only at the highest concentrations. In contrast, combined treatments improved long-term memory even at lower concentrations, revealing consistent multi-compound effects. Bumblebees exposed to caffeine and arginine reduced 24-hour mortality under laboratory conditions. These results identify nectar chemistry as an integrative ecological interface capable of shaping pollinator cognitive performance and survival.
Pellettieri et al. (Fri,) studied this question.