Phylogenetics, Floral Evolution, and Rapid Radiation in the Tropical Monocotyledon Family Costaceae (Zingiberales)

A phylogenetic analysis of the pantropical monocotyledon family Costaceae (Zingiberales) was developed using both molecular (ITS, trrL-F, trrK, maiK) and morphological data. Character sampling was designed to provide phylogenetic signal at the species level. Taxon sampling within the Costaceae was selected to encompass geographical and morphological diversity of the family in order to test the monophyly of taxonomic groups proposed by Schumann [ 39 ] and Maas [ 22 , 23 ] and to define trends in character evolution. The results indicate that the generic taxonomy of Costaceae need to be revised to reflect the phylogenetic hypothesis. Evolutionary trends in floral morphology show that close associations with pollinators have evolved several times from generalist ancestors with an open floral form and that these shifts in floral type to reflect pollination syndromes are associated with species radiations. Bee pollination has evolved once in the family, arising in Africa from an open-flowered ancestor. Bird pollination has evolved multiple times: once from an open-flowered ancestor in Southeast Asia and several times from a bee-pollinated ancestor in the Neotropics. Based on dating exercises using a local 30 molecular clock technique, these shifts to pollination specific floral forms are found to be associated with rapid species radiations, creating clades with significantly more extant species than sister clades. Potential mechanisms for rapid evolution of these clades are discussed in light of the molecular evidence.