REPRODUCTIVE BIOLOGY OF WEEDY AND CULTIVATED MIRABILIS (NYCTAGINACEAE)

The reproductive biology of Mirabilis nyctaginea (Michx.) MacM. contributes to the plant's success as a weed and invader of disturbed habitats whereas that of M. Jalapa L. reflects its success as a cultivar. Plants of M. nyctaginea flowering in early summer produce chasmogamous flowers whereas plants flowering in late summer produce cleistogamous flowers. Plants of both species are self-compatible and flower behavior contributes to self-pollination. The flowers open late in the afternoon and close late the following morning. In M. nyctaginea flowers are effectively pollinated by bees both in the afternoon and morning, and during the night moths are effective pollinators. Mirabilis Jalapa is self-pollinating. Anther closure during rain showers, a result of water droplets falling into open anthers, minimizes pollen loss and is highly adaptive. The reproductive biology of M. nyctaginea and M. Jalapa is contrasted with that of the obligate outcrossing species M. multiflora (Torr.) Gray and M. froebelii (Behr) Greene.