AbstractThe positive electric charge carried by bumblebees (Bombus terrestris) has been shown to affect the movement of pollen between bee and flower during pollination and is likely to affect the sensitivity of bumblebees to electrical stimuli. In this thesis, I investigate how bumblebees gain charge and how this charge affects their interactions with their environment. I show that bumblebees gain an electric charge during flight and when foraging on flowers by triboelectrification. I establish that bumblebees flying outdoors have similar charges to bees flying in the laboratory and further find that charge is affected by relative humidity. Validating previous models of pollen transfer, my measurements also demonstrate that the electric charge carried by bees in nature is sufficient to facilitate pollen transfer during pollination.
Electric charges are measured on the pollinivorous solitary bee species Osmia bicornis and on the social wasp Vespula vulgaris. O. bicornis is found to have similar magnitude positive charges and triboelectrical properties to B. terrestris. Positive charge is not found on V. vulgaris, suggesting that charge generation is an adaptation for pollinivory. This finding supports the hypothesis that cuticular hairs constitute an adaptation enhancing electrostatic pollen transfer.
Mellitophilous flowers advertise their presence to bees using the emission of floral volatiles, with peak volatile emissions corresponding with the peak activity period of their pollinators. In Petunia integrifolia, electrical stimulation by touching the flower with a positively charged nylon ball causes an increase in volatile emissions when using charges representative of highly charged bees. In Antirrhinum majus MTP flowers charge presentation does not result in increased volatile emissions. Finally, I show that P. integrifolia flowers visited by charged bumblebees show an increase in volatile emissions, suggesting that bumblebee charge acts as an indicator of pollinator presence. Previously unappreciated, this electrostatic communication channel is proposed to be adaptive as it enables petunia flowers to coordinate their peak volatile emissions with the activity of their pollinators.
|Date of Award||23 Jan 2020|
|Supervisor||Daniel Robert (Supervisor)|