Male reproductive success and floral trait evolution in animal-pollinated plants

More than 85% of flowering plant species require the services of foraging animal pollinators to transfer male gametes (pollen) to stigmas of potential mates. The vast majority (95-99%) of pollen grains produced by a plant never successfully fertilize ovules, and are instead lost during the complex and chaotic process of pollen transport. For example, some pollen grains fall to the ground as the pollinator picks up pollen or following intense gusts of wind. Other grains are deposited onto the pollinator, but then groomed to pollen carrying baskets or other locations where the grains will no longer contact stigmas of potential mates. Still other pollen grains are buried by pollen from rival males visited subsequently by the pollinator. Recent research suggests that flowering plants have evolved numerous mechanisms to increase the efficiency of the pollen transport process.

A new Review by Minnaar et al. in Annals of Botany explores the intricate “pathway to paternity” in flowering plants, and highlights the evolution of pollination strategies that favor male reproductive success. In particular, they describe bodies of pollinators as arenas for pollen competition where rival males constantly cover or displace competitor pollen. This work provides important new insights about how sexual selection operates in flowering plant populations. The paper is beautifully illustrated with many stunning photos of the pollination process.