Ava-Rose Beech ’21
Studies show that bumble bees may pollinate particular flowers based on microbial concentrations of yeast and bacteria living upon flowers.
Walk outside on any late August day, in the height of summer, and the air is heavy with life. Full with the hum of the millions of ecological relationships continually taking place around us. Mutualistic relationships, in which both organisms benefit from exchanges, are immensely important to ecosystems. However, Avery Russell and Tia-Lynn Ashman’s recent study in Behavioral Ecology finds that there is much more going on than meets the eye when we look into a flower field in mid-August and see a multitude of pollinators buzzing from flower to flower. Research shows that there are even smaller scale symbiotic relationships taking place between plants and pollinators, on a microbial level.
In their work, Russell and Ashman focused specifically on generalist bumble bees, and the flowers generalist bumble bees most frequently pollinate. What makes this research even more exciting is the prospect that these microbes are actually playing a role in determining which flowers bumble bees choose to pollinate, and expanding upon what the scientific community understands about how organisms learn through a combination of innate knowledge and learning.
Russel and Ashman’s experimental work was based upon the hypothesis that these microbial populations living on flowers actually determine which flowers bumble-bees like to
pollinate the most! What is more, the study hypothesizes that microbial differences between flowers play a role in both the innate propensity the bees have to specific flowers, but also that generalist bumble-bees are able to learn to pollinate more biologically favorable flowers based upon the chemical signals these microbes give off. Russel and Ashman tested this exceptional relationship by first culturing a separate yeast and bacteria strain derived from microbial strains from flowers commonly pollinated by generalist bumble bees. After cultivating the yeast and bacteria strains, the researchers conducted a series of 4 experiments to look at the ways in which the different microbes affected which flowers the bees preferred. The first experiment looked at how the bees responded to microbes on artificial flowers. After this, the researchers conducted similar experiments but with real flowers. The last two experiments looked further at questions asked by Russell and Ashman’s hypothesis in regard to the way microbes interact with the bees innate and learned choices in which flowers they pollinate.
The findings of these experiments expand our knowledge of the concept of “plant-bumble bee communication.” The data from these studies indicate that bumble-bees are in fact affected by floral yeast and bacteria in terms of flower choice in pollination. In fact, the studies show that the bees could make even miniscule differentiations in terms of the microbes on a flower. The most interesting finding of Russell and Ashman’s work was that the floral yeast and bacteria play into both the bees innate choice in which flowers to pollinate, but also affected how the bumble-bees learned which flowers were most biologically desirable. The data exemplifies this in experiment 1. The bees can not only detect the microbes on the plant, but also are able to learn which specific microbes signify “flowers with a pollen reward.” This work is immensely exciting in broadening our understanding of the many vital biological relationships that form the basis of healthy ecosystems. Russell and Ashman’s work teaches us that there is more activity than we can possibly perceive taking place beneath the surface, or in this case, on the surface of the flower.
Russell, Avery L, and Tia-Lynn Ashman. “Associative Learning of Flowers by Generalist Bumble Bees Can Be Mediated by Microbes on the Petals.” Behavioral Ecology, vol. 30, no. 3, 2019, pp. 746–755., doi:10.1093/beheco/arz011.
