Floral structure and evolution in Ranunculanae

Abstract

Apomorphic tendencies of unusual features shared by two or more families of the Ranunculanae are: early caducous sepals, congenitally closed gynoecium up to the level of the stigma (but still apically gaping after ovule initiation!), protruding diffuse placentae, transverse fruit dehiscence (in Berberidaceae and Papaveraceae); excessive number of tepal whorls (in some Menispermaceae and Berberidaceae); unisexual flowers, synandry, wet stigmas forming an external compitum (in Menispermaceae and Lardizabalaceae); elaborate nectar-flowers, pollen with tricolpate-multiaperturate series, seeds with elaiosomes (in some Ranunculaceae, Berberidaceae and Papaveraceae). Other unusual features shared by Menispermaceae and Lardizabalaceae may be plesiomorphic or apomorphic: non-peltate carpels, fleshy fruits. Thus, floral structure suggests close relationships between Menispermaceae and Lardizabalaceae as well as Berberidaceae and Papaveraceae. A floral syndrome (probably myiophilous) consisting of small, flat, open, brownish or greenish flowers with short, spathulate, often bilobed staminodes (petals) that present open nectar from their apex occurs in (more or less basal) representatives of four families (except for Papaveraceae). It may be plesiomorphic or represent a basal apomorphic tendency in the Ranunculanae.