Repeated losses of mature corolla bilateral symmetry are not uncommon. Zhong et al. focus on repeated and diverse losses of bilateral symmetry testing whether similar or distinct developmental genetic mechanisms underlie shifts in corolla symmetry in Lamiaceae.
Using phylogenetic, SEM-based developmental and gene expression analyses, repeated losses of mature corolla bilateral symmetry in Lamiaceae are shown to result from various different mechanisms and changes to symmetry genes, including losses of a CYC2 clade and a RAD-like gene from the genome.
Zhong, J., Preston, J. C., Hileman, L. C., & Kellogg, E. A. (2017). Repeated and diverse losses of corolla bilateral symmetry in the Lamiaceae. Annals of Botany, 119(7), 1211–1223. https://doi.org/10.1093/aob/mcx012