mutualism

(myū'chū-ə-lĭz'əm) pronunciation

An association between organisms of two different species in which each member benefits.

mutualistic mu'tu·al·is'tic adj.

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Sci-Tech Encyclopedia: Mutualism

An interaction between two species that benefits both. Individuals that interact with mutualists experience higher sucess than those that do not. Hence, behaving mutualistically is advantageous to the individual, and it does not require any concern for the well-being of the partner. At one time, mutualisms were thought to be rare curiosities primarily of interest to natural historians. However, it is now believed that every species is involved in one or more mutualisms. Mutualisms are thought to lie at the root of phenomena as diverse as the origin of the eukaryotic cell, the diversification of flowering plants, and the pattern of elevated species diversity in tropical forests.

Mutualisms generally involve an exchange of substances or services that organisms would find difficult or impossible to obtain for themselves. For instance, Rhizobium bacteria found in nodules on the roots of many legume (bean) species fix atmospheric nitrogen into a form (NH₃) that can be taken up by plants. The plant provides the bacteria with carbon in the form of dicarboxylic acids. The carbon is utilized by the bacteria as energy for nitrogen fixation. Consequently, leguminous plants often thrive in nitrogen-poor environments where other plants cannot persist. Another well-known example is lichens, in which fungi take up carbon fixed during photosynthesis of their algae associates. See also Nitrogen fixation.

A second benefit offered within some mutualisms is transportation. Prominent among these mutualisms is biotic pollination, in which certain animals visit flowers to obtain resources and return a benefit by transporting pollen between the flowers they visit. A final benefit is protection from one's enemies. For example, ants attack the predators and parasites of certain aphids in exchange for access to the aphids' carbohydrate-rich excretions (honeydew).

Another consideration about mutualisms is whether they are symbiotic. Two species found in intimate physical association for most or all of their lifetimes are considered to be in symbiosis. Not all symbioses are mutualistic; symbioses may benefit both, one, or neither of the partners.

Mutualisms can also be characterized as obligate or facultative (depending on whether or not the partners can survive without each other), and as specialized or generalized (depending on how many species can confer the benefit in question).

Two features are common to most mutualisms. First, mutualisms are highly variable in time and space. Second, mutualisms are susceptible to cheating. Cheaters can be individuals of the mutualist species that profit from their partners' actions without offering anything in return, or else other species that invade the mutualism for their own gain.

Mutualism has considerable practical significance. Certain mutualisms play central roles in humans' ability to feed the growing population. It has been estimated that half the food consumed is the product of biotic pollination. See also Ecology; Plant pathology.

Veterinary Dictionary: mutualism

The biological association of two animals or populations of different species, both of which are benefited by the relationship and sometimes unable to exist without it.

Wikipedia: Mutualism

This article is about the biological term. For the economic theory, see Mutualism (economic theory).

Pollination is a classic example of mutualism.

Mutualism is a biological interaction between individuals of two different species, where both individuals derive a fitness benefit, for example increased survivorship. Similar interactions within a species are known as co-operation. Mutualism may be classified in terms of the closeness of association, the closest being symbiosis, which is often confused with mutualism. One or both species involved in the interaction may be obligate, meaning they cannot survive in the short or long term without the other species. Though mutualism has historically received less attention than other interactions such as predation,^[1] it is very important subject in ecology. Examples include cleaner fish, pollination and seed dispersal, gut flora and nitrogen fixation by fungi.

Classification

Lifelong interactions involving close physical and biochemical contact (known as symbiosis), such as those between plants and mycorrhizal fungi
Briefer, non-symbiotic interactions, such as those between flowering plants and pollinators.
Obligatory or non-obligatory (facultative). For example, bacteria known as rhizobia reproduce either in the soil or in (usually) mutualistic symbiosis with legume plants (Denison & Kiers 2004). Mycorrhizal fungi, on the other hand, can be totally dependent on their plant hosts. microbes often band together for mutual benefit in biofilms to break down solid food sources as in rusticles. The relationship between people and their pets is a non-obligatory mutualism for the human, and, depending on the animal, either obligatory or non-obligatory.

The question how and why species might cooperate has also been addressed philosophically. Gilles Deleuze, for example, is interested in the way this questioned the conception of evolutionism and the notion of linear historical progress.

Examples

Some examples of mutualism are the relationships between bees and flowers, or the example of ants and a shrub brush called Bullhorn Acacia.

In the acacia example, certain ants (e.g. Pseudomyrmex spinicola) nest inside the plant's thorns. In exchange for food and shelter, ants protect acacias from attack by herbivores and competition from other plants. The ants reduce competition by trimming back vegetation that shades the shrub.

Some species of ants also "farm" aphids, protecting them on the plant they eat, and eating the honeydew that the aphids secrete.

A famous land version of symbiosis is the relationship of the Egyptian Plover bird and the crocodile. In this relationship, the bird is well known for preying on parasites that feed on crocodiles. To that end, the crocodile openly invites the bird to hunt on its body, even going so far as to open its jaws to allow the bird enter the mouth safely to hunt the leeches from its gums. For the bird, this relationship not only is a ready source of food, but a safe one considering that few predator species would dare strike at the bird at such proximity to its host.

Many plants will function in a voluntary mutualistic relationship as companion plants, providing each other with shelter, fertilization, the repelling of pests, et cetera. For example, beans may grow up cornstalks as a trellis, while fixing nitrogen in the soil for the corn, as exploited in the three sisters gardening technique.

References

Specific

^ Begon, M., J.L. Harper and C.R. Townsend. 1996. Ecology: individuals, populations, and communities, Third Edition. Blackwell Science Ltd., Cambridge, Massachusetts, USA.

General

Breton, Lorraine M., and John F. Addicott. 1992. Density-Dependent Mutualism in an Aphid-Ant Interaction. Ecology, Vol. 73, No. 6, pp. 2175-2180.
Bronstein, JL. 1994. Our current understand of mutualism. Quarterly Review of Biology 69 (1): 31-51 MAR 1994
Bronstein JL, 2001. The exploitation of mutualisms. Ecology Letters 4 (3): 277-287
Bronstein JL, 2001. The costs of mutualism. American Zoologist 41 (4): 825-839 S
Bronstein JL, Alarcon R, Geber M. 2006. The evolution of plant-insect mutualisms. New Phytologist 172 (3): 412-428
Denison RF, Kiers ET 2004. Why are most rhizobia beneficial to their plant hosts, rather than parasitic? Microbes and Infection 6 (13): 1235-1239 ISSN 1286-4579
DeVries, PJ; and Baker, I. 1989. Butterfly exploitation of an ant-plant mutualism: Adding insult of herbivory. Journal of the New York Entomological Society [J. N.Y. ENTOMOL. SOC.]. Vol. 97, no. 3, pp. 332-340. ISSN 0028-7199
Hoeksema, J.D. & E.M.Bruna. 2000. Pursuing the big questions about interspecific mutualism: a review of theoretical approaches. Oecologia 125:321-330 ISSN 0029-8549
Jahn, G.C. and J.W. Beardsley 2000. Interactions of ants (Hymenoptera: Formicidae) and mealybugs (Homoptera: Pseudococcidae) on pineapple. Proceedings of the Hawaiian Entomological Society 34: 181-185. ISSN 0073-134X
Jahn, Gary C., J. W. Beardsley and H. González-Hernández 2003. A review of the association of ants with mealybug wilt disease of pineapple. Proceedings of the Hawaiian Entomological Society. 36:9-28. ISSN 0073-134X
Noe, R. & P. Hammerstein. 1994. Biological markets: supply and demand determine the effect of partner choice in cooperation, mutualism and mating. Behavioral Ecology and Sociobiology 35:1-11 ISSN 0340-5443
Paszkowski, U. 2006. Mutualism and parasitism: the yin and yang of plant symbioses. Current Opinion on Plant Biology 9 (4): 364-370. ISSN 1369-5266

		Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved. Read more
		Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more
		Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more
		Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Mutualism". Read more

Topics in evolutionary ecology
Patterns of evolution: Convergent evolution • Evolutionary relay • Parallel evolution
Signals: Aposematism • Mimicry • Crypsis
Interactions between species: Mutualism • Predation • Parasitism

mutualism

mutualism

Classification

Examples

See also

References

Specific

General

Further reading