Reproductive biology of P achira aquatica A ubl. ( M alvaceae: B ombacoideae): a tropical tree pollinated by bats, sphingid moths and honey bees

We investigated the reproductive biology, including the floral biology, pollination biology, breeding system and reproductive success, of P achira aquatica , a native and dominant tropical tree of fresh water wetlands, throughout the coastal plain of the G ulf of M exico. The flowers present nocturnal anthesis, copious nectar production and sugar concentration (range 18–23%) suitable for nocturnal visitors such as bats and sphingid moths. The main nocturnal visitors were bats and sphingid moths while bees were the main diurnal visitors. There were no differences in legitimate visitation rates among bats, moths and honey bees. Bats and honey bees fed mainly on pollen while moths fed on nectar, suggesting resource partitioning. Eight species of bats carried pollen but L eptonycteris yerbabuenae is probably the most effective pollinator due to its higher pollen loads. The sphingid moths M anduca rustica, C ocytius duponchel and E umorpha satellitia were recorded visiting flowers. Hand pollination experiments indicated a predominant outcrossing breeding system. Open pollination experiments resulted in a null fruit set, indicating pollen limitation; however, mean reproductive success, according to a seasonal census, was 17 ± 3%; these contrasting results could be explained by the seasonal availability of pollinators. We conclude that P . aquatica is an outcrossing species with a pollination system originally specialized for bats and sphingid moths, which could be driven to a multimodal pollination system due to the introduction of honey bees to tropical America.