A recent study, published as part of a special issue on Plant Reproduction in a Changing Global Environment in Annals of Botany, has shown that drought impacts the floral traits of wildflower species and this in turn affects the foraging preferences of bees.
In a greenhouse experiment, Rose-Person et al subjected two annual wildflower species native to the American Southwest, Phacelia campanularia and Nemophila menziesii, to limited water availability or regular watering schedules and then measured their flower size, nectar volume and nectar sugar concentration. The scientists then released female bees (Osmia lignaria) to study their foraging preferences in a “choice trial”. Individual bees were allowed to freely choose between droughted and non-droughted plants and their choice was recorded and preferences determined.
Rose-Person et al found that when the wildflower species were subjected to drought conditions, their flowers were fewer, smaller, and had reduced, more concentrated nectar. The bees preferred the non-droughted flowers of N. menziesii but had a more complicated response to droughted P. campanularia. For that species, the bees preferred the non-droughted flowers only in the afternoon.
Our findings indicate that bees prefer to visit non-droughted flowers, probably reducing pollination success for drought-stressed plants.
This negative effect on plant-pollinator interaction indicates that drought will reduce wildflower reproduction because the bees will avoid flowers from the drought affected plants. And there could be broader implications.
Rose-Person et al state that “plant–pollinator mutualisms are important for the reproduction of most flowering plant species and for the human food supply.” Indeed, the bee species used in this study is an important pollinator of spring-blooming orchard crops, making the results broadly applicable.
These results indicate that the increased prevalence of droughts associated with climate change might alter the pollination success of drought-stressed plants and, ultimately, the ecology of their interactions with pollinators.
Rose-Person et al further suggest that the reproduction of the insect pollinators themselves might be negatively impacted because they will have less pollen and nectar to provide to their offspring.
READ THE ARTICLE
Rose-Person, A., Santiago, L.S. and Rafferty, N.E. (2025) ‘Drought stress influences foraging preference of a solitary bee on two wildflowers’, Annals of Botany, 135(1-2), pp. 153-164. https://doi.org/10.1093/aob/mcae048
Image: Phacelia campanularia. Canva.
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