Field evidence of strong differential pollen placement by Old World bat-pollinated plants.

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Sympatric plant species that share pollinators potentially compete for pollination and risk interspecific pollen transfer, but this competition can be minimized when plant species place pollen on different areas of the pollinator's body. Multiple studies have demonstrated strong differential pollen placement by sympatric plant species under laboratory conditions; however, field evidence collected in natural settings is less common. Furthermore, it is unknown whether precise pollen placement on the pollinator's body remains constant throughout the foraging period, or if such patterns become diffused over time (e.g. due to grooming). To test the prevalence of differential pollen placement in the wild, we examined a community of five night-blooming plant species in southern Thailand that share common bat pollinators. We mist-netted wild foraging nectar bats and collected pollen samples from four body parts: the crown of the head, face, chest and ventral side of one wing. We also noted the time of pollen collection to assess how pollinator pollen loads change throughout the foraging period. Our findings revealed that most of our plant study species placed pollen on precise areas of the bat, consistent with experimental work, and that patterns of differential pollen placement remained constant throughout the night. This study demonstrates how diverse floral morphologies effectively limit interspecific pollen transfer among Old World bat-pollinated plants under natural conditions. Additionally, interspecific pollen transfer is probably minimal throughout the entire foraging period, since patterns of pollen on the bats' bodies were consistent over time.