Facing a scarcity of pollen, bumblebees will nibble on the leaves of flowerless plants, causing intentional damage in such a way that accelerates the production of flowers, according to a new study, which reports on a previously unknown behavior of bumblebees.

The leaf-damaging bumblebee bites have a drastic effect on plant flowering, compelling some to bloom two weeks to a full month earlier. Although the mechanisms by which deliberate bee damage accelerate flowering remain unclear, the results reveal bumblebees as powerful agents in influencing the local availability of floral resources.

“An encouraging interpretation of the new findings is that behavioral adaptations of flower-visitors can provide pollination systems with more plasticity and resilience to cope with climate change than hitherto suspected,” writes Lars Chittka in a related Perspective. Plants and pollinators rely on one another for survival.

Just as pollinators, like bumblebees, depend on flowers for crucial nutrition, plants need pollinators to reproduce. This symbiotic relationship is kept in balance by the synchronous timing of the emergence of hibernating insects and spring blossoms as spring temperatures rise and the days get longer. But this fragile arrangement is threatened by climate change. For instance, warming early season temperatures could cause pollinators to wake up too soon, before the springtime bloom and without a source of food.

Foteini Pashalidou and colleagues discovered an adaptive strategy used by food-deprived bumblebees to manipulate the timing of a plant’s flowering. Pashalidou et al. observed bumblebee workers from pollen-starved colonies use their mouthparts to cut distinctively shaped holes in the leaves of flowering plants, which resulted in them flowering significantly earlier.

The authors were not able to reproduce the flower-stimulating effects by mimicking the damage on their own, however, suggesting a yet-unknown feature distinct to the bees’ approach. “Understanding the molecular pathways by which one could accelerate flowering by a full month, as reported [by Pashalidou et al.], would be a horticulturalist’s dream,” Chittka writes.

Reference: “Bumble bees damage plant leaves and accelerate flower production when pollen is scarce” by Foteini G. Pashalidou, Harriet Lambert, Thomas Peybernes, Mark C. Mescher and Consuelo M. De Moraes, 22 May 2020, Science.
DOI: 10.1126/science.aay0496