Flowers of the subfamily Lecythidoideae (Lecythidaceae) are showy, spectacular, and highly diversified. Among its ten genera, three genera have polysymmetric flowers and seven have monosymmetric flowers. In monosymmetric flowers, the androecium is proliferated at the dorsal side and curves back to form a hood which is of different colors and structural complexity in different genera. It is believed that the highly diversified floral structure is intimately coevolved with the pollinators. In collaboration with Dr.
Scott Mori from New York Botanical Garden,
Chih-Hua Tsou’ team studied the floral organogenesis of all these ten genera by using SEM and the floral evolutionary trends were interpreted in the context of molecular phylogeny of Lecythidaceae (
Am J Bot 2007 94: 289-301). Flowers of Lecythidoideae is evolved from polysymmetry to monosymmetry via the expression of abaxial dominance and the development of androecium hood, and the evolution is explained as having undergone four levels in regard to the complexity of the floral symmetry.
A reversal from monosymmetry back to polysymmetry is demonstrated in the genus
Cariniana via the gradual weakening of the abaxial dominance and the loss of androecial hood in another paper of Tsou’s team (
Am J Bot 2007 94:716-736).
