Zygomorphy evolved from disymmetry in Fumarioideae

Floral bilateral symmetry (zygomorphy) has evolved at least 70 times during the history of angiosperms, whilst radial symmetry (actinomorphy) is the ancestral and most common state for angiosperms as a whole. Sauquet et al. reconstruct the phylogeny and floral evolution of Papaveraceae (Ranunculales) and find that in this family zygomorphy evolved from a rare, intermediate symmetry form, disymmetry, which is defined by two perpendicular planes of bilateral symmetry. This important transition occurred in subfamily Fumarioideae (fumitories) and is correlated with the loss of a nectar spur.