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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 ?
The seed-ant mutualism, as a general adaptation, is apparently quite resilient.
The solvency effect associated with unemployment, the "crowding-out" effect between mutualism and social security, and the absence of a statistically significant relationship between mutualism and insurance consumption--meaning both variables are independent of each other-are findings that should be born in mind.
The significance of this point to present discussions of mutualism is that the initiators of Mondragon and Desjardin could tap into a pre-existing field of social and cultural meaning within which practices of mutualism and co-operation were meaningful and valuable.
Mutualism is evident in the privatization of state-owned enterprises, in the streamlining of businesses, and particularly in the pace of mergers and acquisitions.
Much of the debate surrounding predator inspection asks whether it is indeed an example of reciprocity or merely a case of by-product mutualism.
Durkheim applies the concept explicitly to separate societies: If, however, in certain cases, peoples tied by no bond, even regarding themselves as enemies, exchange products in a more or less regular manner, it is necessary to see in these facts only simple relations of mutualism having nothing in common with the division of labor.
Christopher Lintz presents uncertainty management as a major factor behind the shift from buffering to mutualism during the protohistoric.
However, large companies also generated diffuse mutualism, lowering the failure rates of companies that had only indirect access to them through the networks of other companies (Barnett and Amburgey, 1990).
Co-operative Trust schools are state-funded schools linked to the Co-operative movement, founded in Lancashire in 1844 which supports common ownership, or mutualism and democratic process where local people have a say in their school.
Herbivore-driven mycorrhizal mutualism in insect-susceptible pinyon pine.
He situates Proudhon's thinking in the nationalist movements of his time, but also writes more theoretically on anarchy as social order and rethinking justice in terms of mutualism.