Bee and floral traits affect the characteristics of the vibrations experienced by flowers during buzz-pollination

Abstract

During buzz pollination, bees use their indirect flight muscles to produce vibrations that are transmitted to the flowers and result in pollen release. Although buzz pollination has been known for >100 years, we are still in the early stages of understanding how bee and floral characteristics affect the production and transmission of floral vibrations. Here we analysed floral vibrations produced by four closely related bumblebee taxa (Bombus spp.) on two buzz-pollinated plants species (Solanum spp.). We measured floral vibrations transmitted to the flower to establish the extent to which the mechanical properties of floral vibrations depend on bee and plant characteristics. By comparing four bee taxa visiting the same plant species, we found that peak acceleration (PA), root mean-squared acceleration (RMS) and frequency varies between bee taxa, but that neither bee size (intertegular distance) or flower biomass (dry weight) affect PA, RMS or frequency. A comparison of floral vibrations of two bee taxa visiting flowers of two plant species, showed that, while bee species affects PA, RMS and frequency, plant species affects acceleration (PA and RMS) but not frequency. When accounting for differences in the transmission of vibrations across the two types of flowers, using a species-specific “coupling factor”, we found that RMS acceleration and peak displacement does not differ between plant species. This suggests that bees produce the same initial acceleration in different plants but that transmission of these vibrations through the flower is affected by floral characteristics.