Reevaluating the evolution of epigyny: Data from phylogenetics and floral ontogeny

A long‐standing perspective of many botanists has been that there is a unidirectional trend in the evolution of ovary position from superior to inferior and that reversals are rare if at all possible. Recent studies that formally investigate the problem of gynoecial diversification in a rigorous phylogenetic context demonstrate that the evolution of ovary position is more complex and dynamic than this traditional view suggested. It is well known that a hypogynous ground plan characterizes a vast majority of angiosperms having superior ovaries and that within a hypogynous ground plan, flowers with inferior ovaries can be produced by a developmental plan termed receptacular epigyny. However, most angiosperms with inferior ovaries have an appendicular‐epigynous ground plan in which a distinctive concavity appears in the center of the floral apex during perianth initiation. Recent investigations have shown that a diverse array of ovary positions ranging from completely inferior to what superficially appear to be superior ovaries, as well as intermediate ovary positions, can all develop from flowers having an appendicular‐epigynous ground plan. A wide range of ovary positions among closely related species can be produced by allometric shifts in development, entailing greater relative growth in either the superior or inferior regions of an ovary. We have termed those ovaries produced via appendicular epigyny that appear superior or nearly superior “pseudosuperior ovaries.” Such ovaries are not developmentally homologous with truly superior ovaries produced via a hypogynous ground plan. We have observed, however, that errors in homology assessment of apparently superior ovaries are not uncommon, such that a number of angiosperm lineages with ovaries that have been termed superior are actually pseudosuperior. Finally, recent studies have demonstrated that reversals from an appendicular‐epigynous to a hypogynous ground plan can occur but are rare.