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

Mutualisms generally involve an exchange of substances or services thatorganisms would find difficult or impossible to obtain for themselves. Forinstance, Rhizobium bacteria found in nodules on the roots of manylegume (bean) species fix atmospheric nitrogen into a form (NH3)that can be taken up by plants. The plant provides the bacteria with carbon inthe form of dicarboxylic acids. The carbon is utilized by the bacteria asenergy for nitrogen fixation. Consequently, leguminous plants often thrive innitrogen-poor environments where other plants cannot persist. Anotherwell-known example is lichens, in which fungi take up carbon fixed duringphotosynthesis of their algae associates.

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

Another consideration about mutualisms is whether they are symbiotic. Twospecies found in intimate physical association for most or all of theirlifetimes 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 (dependingon whether or not the partners can survive without each other), and asspecialized or generalized (depending on how many species can confer thebenefit in question).

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

Mutualism has considerable practical significance. Certain mutualisms playcentral roles in humans' ability to feed the growing population. It hasbeen estimated that half the food consumed is the product of bioticpollination. See Ecology, Plant pathology


Mutual interactions between two species that are beneficial to both species.
References in periodicals archive ?
Nevertheless, it would have been a serious blunder to attempt to abolish mutualist clinics during the upheavals following the revolution.
The Rothbardians and Mutualists have some disagreements over land ownership and theories of value, but their intellectual cross-pollination has brought the groups closer philosophically.
The general strike of 1919 stands out, at least in part, because the anarchists were able to convince the mutualist membership to use tactics viewed as extreme, on behalf of a demand that some saw as revolutionary for the time.
Firstly, Glasman is clearly right that some predominantly (though not exclusively) working-class mutualist organisations such as trade unions and co-operative societies played a key role in early Labour politics, helping to shape Labour's sense of itself as a movement with deep local roots in specific communities.
World-renowned speakers from the cooperative and mutualist movement and the private sector will be in attendance again this year.
For both of these dominant theological parties, the call to abandon Christianity's zero-sum view of other religions and to shift to a non-zero-sum approach-to what is called the Mutualist or Pluralist party--is simply impossible.
Another ambiguity is advocacy of aims such as a "more mutualist vision of shared parenthood" (302).
Looking at the costs and benefits to the tree, not just at a single moment, but in terms of number of offspring produced over a lifetime, the best possible outcome is obtained not by having what we thought was the "good mutualist," but rather by having all four ant species at different life stages - even the so-called parasite, cheater, freeloader scumbag ants," he said.
So, Faeth asks, is the supposed mutualist earning its keep?
Thompson's received views on such matters, though I believe that Morris was more sympathetic than Salmon acknowledges to the radical-democratic mutualist views of anarchists such as Peter Kropotkin and Charlotte Wilson (a point I made some years ago in an edition of Morris' Socialist Diary).
While a case can be made for governments supporting the establishment of co-operatives and other mutualist bodies where no co-operative movement is available to do so, a co-operative movement should be established and the support function devolved to it at the earliest possible opportunity.