Abstract
In the subtropical prefecture of Okinawa, many alien tropical flowers and fruits have been planted along roadways or in gardens. However, the impacts of such planted trees on native pollination and seed dispersal networks are poorly known. In the present study, we investigated diurnal patterns of nectar secretion and pollinator visits to flowers on coral trees (Erythrina variegata L.). Although the coral tree is known as a diurnal bird-pollinated plant, several taxa of pollinators, such as birds, insects, and flying foxes were observed on the flowers of planted coral trees on Okinawa-jima Island. Flowers began to open in the morning, and nectar was only secreted during the daytime. In 60% of all flowers, almost all nectar was harvested by diurnal flower visitors, such as white eyes (Zosterops japonicas [Temminck & Schlegel]), by evening. The remaining nectar of unharvested flowers (30% of total flowers) was depleted by nocturnal Ryukyu flying foxes (Pteropus dasymallus Temminck) during the nighttime. Although planted coral trees provide food resources for the endangered Ryukyu flying fox in urbanized areas, these planted trees may rob native plant species of opportunities for pollination or seed dispersal. In Okinawa, which harbors many vertebrate-pollinated plants, the networks between plants and flying foxes/birds must be considered when selecting trees to plant along roadways or in green spaces.
