Flowering phenology, floral biology, breeding system, and pollination in the andromonoecious Commelina diffusa (Commelinaceae)

Abstract

Occurrence of male and bisexual flowers (andromonoecy) in a species is thought to be an adaptation to enhance reproductive success through increasing male function or by diverting resources otherwise used for the formation of pistils. Commelina diffusa Burm. f. is a pantropical, herbaceous, and andromonoecious species from the family Commelinaceae. A typical inflorescence comprises male and bisexual flowers enclosed within a spathe. Morphology of the different floral types, floral phenology, pollen viability, pollen production, and mating system were studied in this annual, bearing small fruits. Being nectarless, pollen is the only reward for the pollinators in this species. The number of fruits developing was found to influence the gender of the subsequent flowers within the spathe. The floral visitors, including members of Diptera and Hymenoptera, facilitate outcrossing and may mediate geitonogamous selfing as well. Delayed selfing takes place when floral organs intertwine as the flower fades. Andromonoecy in itself does not promote outcrossing, but it may be advantageous to present pollen in more flowers, thereby attracting and feeding more insects and potentially increase male function.