Invasive honeybees exacerbate the low reproductive success of a bat-pollinated tree

Some bat species play a crucial role as the main effective pollinators of many flowering plants. Nevertheless, other floral visitors may act as antagonists, affecting the reproductive success of these plants. In this study, we investigated some potential causes of the extremely low production of fruits of Crescentia alata, a neotropical tree supposedly pollinated by bats that is heavily visited by the introduced honeybee Apis mellifera in Guerrero, southern Mexico. Our results indicate that C. alata had an extremely low natural fruit set (0.2%) and total pollen limitation, probably due to multiple intrinsic factors, including a complete self-incompatible system, low herkogamy, and incomplete dichogamy; as well as extrinsic factors such as the high pollen removal associated with the numerous visits of the invasive honeybees before the arrival of bats, which were the most effective pollinators of this plant. Nectarivorous bat conservation through forest restoration, as well as a decrease of managed beehives and the plantation of genetically diverse individuals, are proposed as strategies to minimize the low reproduction of this neotropical tree of great importance to humans and to the maintenance of tropical dry forests.