Abstract
Botanists have long identified angiosperm species with bilaterally symmetrical (zygomorphic) flowers as having more specialized pollination interactions than species with radially symmetrical (actinomorphic) flowers. Zygomorphic flowers facilitate more precise contact with pollinators, guide pollinator behavior, and exclude less effective pollinators. However, to our knowledge, the basic idea that zygomorphic flowers are visited by a smaller subset of available pollinators has not been broadly evaluated. We compiled data on 32,901 plant-pollinator associations in 159 communities around the world and classified the plants’ floral symmetry. Globally and within individual communities, we found that plant species with zygomorphic flowers are visited by fewer pollinators. We also found that that the structures of pollination networks differ for plants with different floral symmetry, in ways that may arise from differences in pollinator diversity. These results may explain associations between zygomorphy and diversification, and imply that species with zygomorphic flowers face greater risks of extinction due to pollinator loss.
Footnotes
Update to reflect final journal submission