Bee community composition, but not diversity, is influenced by floret size in cultivated sunflowers

Authors: Yoshimura Ferguso, Mary; MALLINGER, RACHEL - University Of Florida; Prasifka, Jarrad

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2021
Publication Date: 11/26/2021
Citation: Yoshimura Ferguson, M.E., Mallinger, R., Prasifka, J.R. 2021. Bee community composition, but not diversity, is influenced by floret size in cultivated sunflowers. Apidologie. 52:1210-1222. https://doi.org/10.1007/s13592-021-00897-z.
DOI: https://doi.org/10.1007/s13592-021-00897-z

Interpretive Summary: More bees visit sunflowers with shallower flowers because the nectar in the flowers is easier to reach with their tongues. But it is not clear from earlier research whether flower size affects the diversity of composition of bee species pollinating sunflowers. In two years and two planting dates (early and late), bees were collected and counted, along with measurements of flower size and nectar. Sunflowers with larger and smaller flowers were visited by equally diverse groups of bees, but the number and type of bees were influenced by flower size. Unlike most other wild bees, bumble bees were only common in the late-planted sunflowers, and preferred to visit sunflowers with deeper flowers. Some smaller bees appeared to change their preference when bumble bees were common, suggesting interactions between small- and large-bodied bees may be important.

Technical Abstract: Nectar-related traits influence the number of bee visits to sunflowers, but the effects of floret size on the diversity and composition of bee communities is unknown. In four year × planting date combinations, bees were collected from sunflowers with small (<7.5mm), medium (7.5-9mm), or large (>9mm) florets, and counts of foraging bees were used to clarify bee responses to plant traits. No effect of floret size on diversity of foraging bees was found, but associations of bee tongue length and floret size led to differences in the communities foraging on sunflowers with small, medium or large florets. Though most wild bees preferred to forage on plants with more nectar and smaller florets (˜ easier access to nectar), Bombus spp. showed an opposite response to floret size, foraging preferentially on lines with large florets. Changes in Melissodes spp. foraging preference in the presence of Bombus spp. also suggest interactions between small- and large-bodied bees may be important.