Question

Although successful with highly elaborate flowers and numerous species, what aspect of monocot flowers are considered ancestral?

Answer 1

Traditionally, the flowering plants have been divided into two major groups, Dicots and Monocots.  Monocot flowers are ancestral can explain many aspects of angiosperm diversification, beginning with the early embryo itself. The key features of monocot flowers include the typical monocot groundplan of trimerous pentacyclic flowers and a character suite related to carpel fusion, including postgenital fusion between carpels and the presence of septal nectaries. It is likely that the trimerous-pentacyclic flower represents a major synapomorphy of monocots. This groundplan is absent from the closest relatives of monocots. The morphogenetic studies and analysis of character correlations in monocots lead to a hypothesis that the ancestral monocot conditions were postgenital fusion between carpels and presence of septal nectaries.  A gynoecium with free carpels represents a derived condition in monocots and evolved independently in three unrelated groups (Triuridaceae, Arecaceae, Alismatales), with several gains of apocarpy in Alismatales and palms. All three monocot groups that include free-carpellate species show significant variation in their individual floral groundplans. The free-carpellate condition evolved several times during the course of monocot evolution.