Global distribution and evolutionary transitions of floral symmetry in angiosperms

Floral symmetry plays a crucial role in plant-pollinator interactions and has remarkable impacts on angiosperm evolution. However, the spatiotemporal patterns in floral symmetry and drivers of these patterns remain poorly known. Here, using global distributions and floral symmetry data of 280,140 angiosperm species, we presented the global geographic and evolutionary patterns of floral symmetry composition and demonstrated the climatic drivers of these patterns. We found that the frequency of actinomorphic (radial) species increased with latitude, while that of zygomorphic (bilateral) species decreased. Solar radiation, present-day temperature and Quaternary temperature change explained the geographic variation in floral symmetry. Evolutionary transitions from actinomorphy to zygomorphy dominated floral symmetry evolution, although the rate of this transition decreased through the Cenozoic associated with decreasing paleo-temperature. Our study provides novel insights into the ecology and evolution of angiosperm floral symmetry and suggests that climate change may influence species distributions via its effect on floral symmetry.