Inflorescence patterns in the woody Brazilian genus Diplusodon (Lythraceae)

The Brazilian genus Diplusodon is the second largest genus within Lythraceae. Their 85 species occupy diverse habitats within the ‘cerrado’ vegetation, and range from shrubs and treelets to dwarf, xylopodium-bearing subshrubs. A comparative-morphological survey of their inflorescence structures using Trollian typology is here presented, as well as some evolutionary considerations drawn from mapping inflorescence characters onto a preliminary phylogeny. The inflorescences of Diplusodon are mostly polytelic, ranging from single racemes to more or less complex double-, triple-, and multiple-racemes. Frondose, compound racemes are plesiomorphic within the genus. Nevertheless, an array of derived features has been found among their species, including production of lateral cymes, proliferation of the main axis, diverse patterns of internode elongation, reduction of subtending leaves to bracts, development of accessory branches, paedomorphic flowering, and, in three species, reversion to monotely.