Does body size predict the buzz‐pollination frequencies used by bees?. Issue 8 (21st March 2019)

• Record Type: Journal Article
• Authors: De Luca, Paul A.; Buchmann, Stephen; Galen, Candace; Mason, Andrew C.; Vallejo‐Marín, Mario
• Is Part Of: Ecology and evolution. Volume 9:Issue 8(2019)
• Page Start: 4875
• Page End: 4887
• Publication Date: 2019-03-21
• Subjects: Anthophila -- buzz ratio -- floral vibrations -- frequency -- Pedicularis -- Solanum; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.5092
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Body size is an important trait linking pollinators and plants. Morphological matching between pollinators and plants is thought to reinforce pollinator fidelity, as the correct fit ensures that both parties benefit from the interaction. We investigated the influence of body size in a specialized pollination system (buzz‐pollination) where bees vibrate flowers to release pollen concealed within poricidal stamens. Specifically, we explored how body size influences the frequency of buzz‐pollination vibrations. Body size is expected to affect frequency as a result of the physical constraints it places on the indirect flight muscles that control the production of floral vibrations. Larger insects beat their wings less rapidly than smaller‐bodied insects when flying, but whether similar scaling relationships exist with floral vibrations has not been widely explored. This is important because the amount of pollen ejected is determined by the frequency of the vibration and the displacement of a bee's thorax. We conducted a field study in three ecogeographic regions (alpine, desert, grassland) and recorded flight and floral vibrations from freely foraging bees from 27 species across four families. We found that floral vibration frequencies were significantly higher than flight frequencies, but never exceeded 400 Hz. Also, only flight frequencies were negatively correlated with body size. As a bee's size increased, its buzz ratio (floral frequency/flight frequency) increased such that only the largest bees were capable of generating floral vibration frequencies that exceeded double that of their flight vibrations. These results indicate size affects the capacity of bees to raise floral vibration frequencies substantially above flight frequencies. This may put smaller bees at a competitive disadvantage because even at the maximum floral vibration frequency of 400 Hz, their inability to achieve comparable thoracic displacements as larger bees would result in generating vibrations with lower amplitudes, and thus less total pollen ejected for the same foraging effort. Abstract : We investigated the influence of body size on the frequencies of buzz pollination vibrations in bees across three different eco‐habitats. We found that body size was significantly negatively correlated with flight frequency but not with floral vibration frequency. Only larger bees produced floral vibrations that approached or exceeded twice that of their flight vibrations.