Pollination by Animals

Abstract Most species of flowering plants depend on animals, such as bees, to move their pollen and enable sexual reproduction, and most animal pollinators, in turn, depend on flowers as sources of food or other materials. Although the interaction is mutualistic, benefitting both plants and animals, it is not cooperation, because the best ‘interests’ of the two partners differ. Animal pollination is critical for crop and natural ecosystems and plays central roles in plant ecology and evolution. In particular, selection imposed by animal pollinators is thought to have driven the evolution of much of the floral diversity we see today. Most plant–pollinator relationships are not specialised, one‐to‐one mutualisms – a fact that should make pollination networks somewhat resilient to species extinctions. Nevertheless, recent pollinator declines have given rise to concerns about loss of pollination services to crops and wild plant populations. Key Concepts: Most flowering plant species depend on animals to transfer pollen from anthers (the male organs of flowers) to stigmas (the female organs) in order to produce seeds. Pollinating animals visit flowers to obtain resources: usually nectar or pollen, but sometimes oils, fragrances, resins or oviposition sites. The divergent ‘interests’ of plants and pollinators in the interaction explain such phenomena as unrewarding flowers and nectar‐robbing insects. Recent pollinator declines are causing concern about the maintenance of pollination services to crops and wild plants. Pollination webs illustrating the linkages among plants and pollinators within a community show that reciprocally specialised interactions are rare. Numerous studies show that pollinators can exert selection on plant traits, but selection by plants on pollinator traits has been harder to demonstrate. Pollinators play an important role in the process of reproductive isolation and speciation in flowering plants.