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.

花对称性（Floral symmetry）在植物-传粉者互作中扮演关键角色，并对被子植物（angiosperm）的演化具有显著影响。然而，花对称性的时空格局及其驱动因素仍知之甚少。本研究基于280,140种被子植物的全球分布及花对称性数据，揭示了花对称性组成的全球地理与演化格局，并阐明了这些格局的气候驱动因素。研究发现，辐射对称（actinomorphic）物种的频率随纬度升高而增加，而两侧对称（zygomorphic）物种的频率则随之降低。太阳辐射、现代温度及第四纪（Quaternary）温度变化可解释花对称性的地理变异。从辐射对称型（actinomorphy）到两侧对称型（zygomorphy）的演化转变主导了花对称性的演化，尽管这一转变速率在新生代（Cenozoic）期间随古温度降低而下降。本研究为被子植物花对称性的生态学与演化研究提供了新的见解，并提示气候变化可能通过影响花对称性进而作用于物种分布。