Pollination by Animals


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.

Keywords: angiosperms; evolution; mutualism; pollination web; natural selection; specialisation

Figure 1.

Yuccas and yucca moths. (a) A female moth collects pollen with her mouthparts, after which she flies to a different plant (this is critical as yuccas are completely or partially self‐incompatible). (b) The female then oviposits into the ovary of a new flower, after which she places pollen on the stigma. (c) Larvae develop within a single fruit and consume some, but not all, of its seeds. The plants abort fruits into which too many eggs are laid, thus exerting some control over ‘cheaters’ that devour most or all the seeds. Reproduced from Riley ().

Figure 2.

A pollination web. Sampling of flower visitors over one fortnight in upland vegetation on the island of Mauritius, in the tropical Indian Ocean, yielded this web of interactions among pollinators (numbered along the top, with width of each coloured rectangle proportional to relative abundance of that species) and plants (along the bottom). Width of the wedge connecting animals to plants indicates the relative frequency of their interaction. The pollinators are coded as follows: red=Hymenoptera other than ants, magenta=Gekkonidae (one species, Phelsuma cepediana, blue‐tailed day gecko), blue=Diptera, dark green=Aves (one species, number 160, Zosterops mauritianus, grey white eye), green=Hemiptera, orange=Formicidae and yellow=Lepidoptera. The 32 plant species were visited by a mean of 3.1 pollinator species each, whereas the 28 pollinator species visited a mean of 2.6 plants each. This web is representative of pollination webs studied to date in that it contains a range of species from specialists to generalists, with specialists tending to interact with generalists rather than with other specialists. Reproduced from Kaiser ().

Figure 3.

Disruptive natural selection on width of the flower tube (corolla) in Ipomopsis. In rare years, hawkmoths join hummingbirds as pollinators, and selection favours the narrowest and widest corollas rather than intermediates. This situation recalls a scenario for pollinator‐mediated speciation without geographical isolation. There is no significant selection on corolla length. Reproduced from Campbell ().



Aizen MA, Sabatino M and Tylianakis JM (2012) Specialization and rarity predict nonrandom loss of interactions from mutualist networks. Science 335: 1486–1489.

Aldridge G and Campbell DR (2007) Variation in pollinator preference between two Ipomopsis contact sites that differ in hybridization rate. Evolution 61: 99–110.

Armbruster WS (2009) Evolutionary and ecological aspects of specialised pollination: views from the arctic to the tropics. In: Waser NM and Ollerton J (eds) Plant–Pollinator Interactions: From Specialization to Generalization, pp. 260–282. Chicago, IL: University of Chicago Press.

Bernasconi G, Ashman T‐L, Birkhead TR et al. (2004) Evolutionary ecology of the prezygotic stage. Science 303: 971–975.

Biesmeijer JC, Roberts SPM, Reemer M et al. (2006) Parallel declines in pollinators and insect‐pollinated plants in Britain and the Netherlands. Science 313: 351–354.

Buchmann SL and Nabhan GP (1997) Services provided by pollinators. In: Daily GC (ed.) Nature's Services: Societal Dependence on Natural Ecosystems, pp. 133–150. Washington, DC: Island Press.

Cameron SA, Lozier JD, Strange JP et al. (2011) Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Sciences of the USA 108: 662–667.

Campbell DR (2003) Natural selection in Ipomopsis hybrid zones: Implications for ecological speciation. New Phytologist 161: 83–90.

Campbell DR, Waser NM and Pederson GT (2002) Predicting patterns of mating and rates of hybridization from pollinator behavior. American Naturalist 159: 438–450.

Costanza R, d'Arge R, de Groot R et al. (1997) The value of the world's ecosystem services and natural capital. Nature 387: 253–260.

Ehrlén J, Münzbergova Z, Diekmann M and Eriksson O (2006) Long‐term assessment of seed limitation in plants: Results from an 11‐year experiment. Journal of Ecology 94: 1224–1232.

Gallai N, Salles J‐M, Settele J and Vaissière BE (2009) Economic valuation of the vulnerability of world agriculture confronted with pollinator decline. Ecological Economics 68: 810–821.

Grimaldi DA (1999) The co‐radiations of pollinating insects and angiosperms in the Cretaceous. Annals of the Missouri Botanical Garden 86: 373–406.

Ippolito A, Wilson Fernandes G and Holtsford TP (2004) Pollinator preferences for Nicotiana alata, N. forgetiana, and their F1 hybrids. Evolution 58: 2534–2544.

Kaiser CN (2006) Functional Integrity of Plant‐Pollinator Communities in Restored Habitats in Mauritius. PhD Dissertation, Universität Zürich, Zürich, Switzerland.

Kaiser‐Bunbury CN, Muff S, Memmott J, Müller CB and Caflisch A (2010) The robustness of pollination networks to the loss of species and interactions: a quantitative approach incorporating pollinator behaviour. Ecology Letters 13: 442–452.

Klein A‐M, Vaissière BE, Cane JH et al. (2006) Importance of pollinators in changing landscapes for world crops. Proceedings of the Royal Society B: Biological Sciences 274: 303–313.

Knight TM, Steets JA, Vamosi JC et al. (2005) Pollen limitation of plant reproduction: pattern and process. Annual Review of Ecology, Evolution, and Systematics 36: 467–497.

Memmott J, Waser NM and Price MV (2004) Tolerance of pollination networks to species extinctions. Proceedings of the Royal Society B: Biological Sciences 271: 2605–2611.

National Research Council (2007) Status of Pollinators in North America. Washington, DC: National Academies Press.

Ollerton J, Alarcón R, Waser NM et al. (2009) A global test of the pollination syndrome hypothesis. Annals of Botany 103: 1471–1480.

Ollerton J and Cranmer L (2002) Latitudinal trends in plant‐pollinator interactions: are tropical plants more specialised? Oikos 98: 340–350.

Ollerton J, Winfree R and Tarrant S (2011) How many flowering plants are pollinated by animals? Oikos 120: 321–326.

Pellmyr O (2003) Yuccas, yucca moths, and coevolution: a review. Annals of the Missouri Botanical Garden 90: 35–55.

Petanidou T, Kallimanis AS, Tzanopoulos J, Sgardelis SP and Pantis JP (2008) Long‐term observation of a pollination network: fluctuation in species and interactions, relative invariance of network structure and implications for estimates of specialization. Ecology Letters 11: 564–575.

Price MV, Campbell DR, Waser NM and Brody AK (2006) Bridging the generation gap in plants: from parental fecundity to offspring demography. Ecology 89: 1596–1604.

Ramírez SR, Eltz T, Fujiwara MK et al. (2011) Asynchronous diversification in a specialized plant–pollinator mutualism. Science 333: 1742–1746.

Riley CV (1892) The yucca moth and yucca pollination. Annual Report of the Missouri Botanical Garden 1892: 99–158.

Rønsted N, Weiblen GD, Cook JM et al. (2005) 60 million years of co‐divergence in the fig–wasp symbiosis. Proceedings of the Royal Society B: Biological Sciences 272: 2593–2599.

Strauss SY and Irwin RE (2004) Ecological and evolutionary consequences of multispecies plant–animal interactions. Annual Review of Ecology, Evolution, and Systematics 35: 435–466.

Further Reading

Bronstein JL, Alarcón R and Geber M (2006) The evolution of plant‐insect mutualisms. New Phytologist 172: 412–428.

Buchmann SL and Nabhan GP (1996) The Forgotten Pollinators. Washington, DC: Island Press.

Chittka L and Raine NE (2006) Recognition of flowers by pollinators. Current Opinion in Plant Biology 9: 428–435.

Chittka L and Thomson JD (eds) (2001) Cognitive Ecology of Pollination: Animal Behavior and Floral Evolution. Cambridge, UK: Cambridge University Press.

Harder LD and Barrett SCH (eds) (2006) Ecology and Evolution of Flowers. Oxford, UK: Oxford University Press.

Proctor M, Yeo P and Lack A (2003) The Natural History of Pollination. London, UK: HarperCollins.

Real LA (ed.) (1983) Pollination Biology. Orlando, FL: Academic Press.

Waser NM and Campbell DR (2004) Ecological speciation in flowering plants. In: Dieckmann U, Metz H, Doebeli M and Tautz D (eds) Adaptive Speciation, pp. 264–277. Cambridge, UK: Cambridge University Press.

Waser NM and Ollerton J (eds) (2006) Plant‐pollinator Interactions: From Specialization to Generalization. Chicago, IL: University of Chicago Press.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Waser, Nickolas M, and Forrest, Jessica RK(Apr 2014) Pollination by Animals. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0003163.pub3]