|
Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other. Similar interactions within a species are known as co-operation. Mutualism can be contrasted with interspecific competition, in which each species experiences ''reduced'' fitness, and exploitation, or parasitism, in which one species benefits at the ''expense'' of the other. Mutualism is a type of symbiosis. Symbiosis is a broad category, defined to include relationships that are mutualistic, parasitic, or commensal. Mutualism is only one ''type''. A well-known example of mutualism is the relationship between ungulates (such as bovines) and bacteria within their intestines. The ungulates benefit from the cellulase produced by the bacteria, which facilitates digestion; the bacteria benefit from having a stable supply of nutrients in the host environment. This can also be found in many many different symbiotic relationships. Mutualism plays a key part in ecology. For example, mutualistic interactions are vital for terrestrial ecosystem function as more than 48% of land plants rely on mycorrhizal relationships with fungi to provide them with inorganic compounds and trace elements. In addition, mutualism is thought to have driven the evolution of much of the biological diversity we see, such as flower forms (important for pollination mutualisms) and co-evolution between groups of species.〔Thompson, J. N. 2005 The geographic mosaic of coevolution. Chicago, IL: University of Chicago Press.〕 However mutualism has historically received less attention than other interactions such as predation and parasitism.〔Bronstein, JL. 1994. Our current understand of mutualism. Quarterly Review of Biology 69 (1): 31–51 March 1994〕〔Begon, M., J.L. Harper, and C.R. Townsend. 1996. ''Ecology: individuals, populations, and communities'', Third Edition. Blackwell Science Ltd., Cambridge, Massachusetts, USA.〕 Measuring the exact fitness benefit to the individuals in a mutualistic relationship is not always straightforward, particularly when the individuals can receive benefits from a variety of species, for example most plant-pollinator mutualisms. It is therefore common to categorise mutualisms according to the closeness of the association, using terms such as obligate and facultative. Defining "closeness," however, is also problematic. It can refer to mutual dependency (the species cannot live without one another) or the biological intimacy of the relationship in relation to physical closeness (''e.g.'', one species living within the tissues of the other species).〔Ollerton, J. 2006. "Biological Barter": Interactions of Specialization Compared across Different Mutualisms. pp. 411–435 in: Waser, N.M. & Ollerton, J. (Eds) Plant-Pollinator Interactions: From Specialization to Generalization. University of Chicago Press.〕 The term "mutualism" was introduced by Pierre-Joseph van Beneden in 1876.〔van Beneden, Pierre-Joseph (1876). Animal parasites and messmates. London, Henry S. King.〕 ==Types of relationships== Mutualistic transversals can be thought of as a form of "biological barter"〔 in mycorrhizal associations between plant roots and fungi, with the plant providing carbohydrates to the fungus in return for primarily phosphate but also nitrogenous compounds. Other examples include rhizobia bacteria that fix nitrogen for leguminous plants (family Fabaceae) in return for energy-containing carbohydrates.〔Denison RF, Kiers ET 2004. Why are most rhizobia beneficial to their plant hosts, rather than parasitic. Microbes and Infection 6 (13): 1235–1239〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mutualism (biology)」の詳細全文を読む スポンサード リンク
|