A sensory bias overrides learned preferences of bumblebees for honest signals in Mimulus guttatus

Insect pollinators readily learn olfactory cues, and this is expected to select for 'honest signals' that provide reliable information about floral rewards. However, plants might alternatively produce signals that exploit pollinators' sensory biases, thereby relaxing selection for signal honesty. We examined the innate and learned preferences of Bombus impatiens for Mimulus guttatus floral scent phenotypes corresponding to different levels of pollen rewards in the presence and absence of the innately attractive floral volatile compound beta -trans-bergamotene. Bees learned to prefer honest signals after foraging on live M. guttatus flowers, but only exhibited this preference when presented floral scent phenotypes that did not include beta -trans-bergamotene. Our results suggest that a sensory bias for beta -trans-bergamotene overrides the ability of B. impatiens to use honest signals when foraging on M. guttatus. This may represent a deceptive pollination strategy that allows plants to minimize investment in costly rewards without incurring reduced rates of pollinator visitation.

Automated summary

Insect pollinators have the ability to learn olfactory cues and prefer 'honest signals' for floral rewards, but might be influenced by sensory biases towards certain compounds. This study suggests that a sensory bias for beta-trans-bergamotene can override the ability of Bombus impatiens to use honest signals when foraging on Mimulus guttatus flowers, potentially representing a deceptive pollination strategy for plants.