Evolution of floral zygomorphy in androecium and corolla in Solanaceae

In Solanaceae, a group dominated by actinomorphic-flowered species, floral zygomorphy is frequently observed among the early-branching clades. Morphological studies indicated that a zygomorphic androecium is much more common than a zygomorphic corolla in the family. Ontogenic studies suggested the evolution of floral zygomorphy in these two whorls is independent. Here, we have examined the evolution of floral symmetry in the androecium and corolla in Solanaceae. The character states of floral symmetry were assembled for androecium and corolla separately, and ancestral state reconstructions were carried out at both the genus and species levels for Solanaceae and its outgroups. Correlation tests were performed to determine whether the presence of floral zygomorphy in the androecium and corolla is correlated. The ancestral state reconstructions suggest the flower of the most recent common ancestor of Solanaceae is likely zygomorphic in the androecium but actinomorphic in the corolla. Multiple losses and gains of floral zygomorphy in androecium and corolla explain the existing pattern of floral symmetry in Solanaceae. A significant positive correlation between the possession of floral zygomorphy in the androecium and corolla of Solanaceae was detected. Floral zygomorphy likely has evolved in androecium and corolla along separate evolutionary trajectories, and zygomorphy in the androecium may be a precursor for the many gains of zygomorphy in the corolla in Solanaceae.