Flower Orientation and Color Change in Quisqualis indica and Their Possible Role in Pollinator Partitioning

Quisqualis indica (Combretaceae), an ornamental climber in Israel, has white and horizontally oriented flowers that open at dusk and, on the following day, change to pink and later to red, simultaneously changing orientation to become pendulous. The flowering period for each flower is 3 days. At night, white flowers are visited by hawkmoths, while the red flowers are neglected by night visitors. During the day, pink and red flowers are visited by a wide range of visitors: solitary bees, honeybees, flies, and sunbirds. Pollen grains germinate well on the stigmatic fluid during the first few hours, but germination is reduced during the day. Pollen tubes do not penetrate into the style, and seeds are not produced in Israel. Nectar flow begins at flower dehiscence, reaches its peak at early morning, and then is absorbed by the flower. During the first hours of blooming, the flower is typically "hawkmoth" but, by the next morning, attracts visitors other than hawkmoths.