Temporal configuration and modality of components determine the performance of bumble bees during the learning of a multimodal signal

Across communicative systems, the ability of compound signals to enhance receiver's perception and decoding is a potent explanation for the evolution of complexity. In nature, complex signaling involves spatiotemporal variation in perception of signal components; yet, how the synchrony between components affects performance of the receiver is much less understood. In the coevolution of plants and pollinators, bees are a model for understanding how visual and chemical components of floral displays may interact to influence performance. Understanding whether the temporal dimension of signal components impacts performance is central for evaluating hypotheses about the facilitation of information processing and for predicting how particular trait combinations function in nature. Here, I evaluated the role of the temporal dimension by testing the performance of bumble bees under restrained conditions while learning a bimodal (olfactory and visual) stimulus. I trained bumble bees under six different stimuli varying in their internal synchrony and structure. I also evaluated the acquisition of the individual components. I show that the temporal configuration and the identity of the components impact their combined and separate acquisition. Performance was favored by partial asynchrony and the initial presentation of the visual component, leading to higher acquisition of the olfactory component. This indicates that compound stimuli resembling the partially synchronous presentation of a floral display favor performance in a pollinator, thus highlighting the time dimension as crucial for the enhancement. Moreover, this supports the hypothesis that the evolution of multimodal floral signals may have been favored by the asynchrony perceived by the receiver during free flight.