Pollen landscape saturation on pollinator bodies reduces pollen deposition by subsequently visited bat‐pollinated flowers

Abstract Sexual selection in flowering plants often operates through male–male competition, yet the mechanisms underlying this phenomenon remain difficult to demonstrate. One potential arena for such competition is pollen placement on pollinators, where pollen grains from different donors interact within a dynamic pollen landscape on the pollinator's body that is shaped by pollinator morphology and behaviour. In pollinators that groom infrequently, such as nectar‐feeding bats, pollen loads may accumulate over successive floral visits, eventually saturating available pollen‐deposition sites on the pollinator's body and precluding the placement of newly acquired pollen. Here, we tested the hypothesis that pollen landscape saturation on the pollinator's body reduces pollen transfer from the last visited flower to stigmas and consequently influences male reproductive success. Using a controlled experimental setup, we quantified pollen deposition by the nectar‐feeding bat Anoura geoffroyi on stigmas of Macrocarpaea glabra flowers. By tracking quantum dot–labelled pollen with different colours, we compared transfer from a single male‐phase to a female‐phase flower by pollen‐free bats with that by bats saturated after five prior visits to male‐phase flowers. Single flowers that were visited by pollen‐free bats deposited over twice as much pollen as single flowers that were visited by pollen‐saturated bats. These results demonstrate that pollen landscapes on pollinator bodies are highly dynamic and can become saturated, leading to pollen preclusion and reduced pollen transfer from the last visited flower to stigmas. Our findings provide direct evidence that pollen landscape saturation can influence male–male competition in plants and highlight pollinator‐mediated pollen dynamics as an important yet underexplored component of sexual selection in flowering plants. Read the free Plain Language Summary for this article on the Journal blog.