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In biology, coevolution is "the change of a biological object triggered by the change of a related object". In other words, when changes in at least two species' genetic compositions reciprocally affect each other’s evolution, coevolution has occurred. There is evidence for coevolution at the level of populations and species. Charles Darwin briefly described the concept of coevolution in ''On the Origin of Species'' (1859) and developed it in detail in ''Fertilisation of Orchids'' (1862). It is likely that viruses and their hosts coevolve in various scenarios.〔C.Michael Hogan. 2010. (Encyclopedia of Earth ). Editors: Cutler Cleveland and Sidney Draggan〕 However, there is little evidence of coevolution driving large-scale changes in Earth's history, since abiotic factors such as mass extinction and expansion into ecospaces seem to guide the shifts in the abundance of major groups. One proposed specific example was the evolution of high-crowned teeth in grazers when grasslands spread through North America - long held up as an example of coevolution. We now know that these events happened independently. Coevolution can occur at many biological levels: it can be as microscopic as correlated mutations between amino acids in a protein or as macroscopic as covarying traits between different species in an environment. Each party in a coevolutionary relationship exerts selective pressures on the other, thereby affecting each other's evolution. Coevolution of different species includes the evolution of a host species and its parasites (host–parasite coevolution), and examples of mutualism evolving through time. Evolution in response to abiotic factors, such as climate change, is not biological coevolution (since climate is not alive and does not undergo biological evolution). The general conclusion is that coevolution may be responsible for much of the genetic diversity seen in normal populations including: blood-plasma polymorphism, protein polymorphism, histocompatibility systems, etc.〔Anderson, R., and May, R. (1982), Coevolution of hosts and parasites, Parasitology, Cambridge Journals, retrieved from http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=4133104〕 The parasite/host relationship probably drove the prevalence of sexual reproduction over the more efficient asexual reproduction. It seems that when a parasite infects a host, sexual reproduction affords a better chance of developing resistance (through variation in the next generation), giving sexual reproduction viability for fitness not seen in the asexual reproduction, which produces another generation of the organism susceptible to infection by the same parasite.〔Editors (2011), Sexual reproduction works thanks to ever-evolving host, parasite relationships: study, Physorg, retrieved fromhttp://phys.org/news/2011-07-sexual-reproduction-ever-evolving-host-parasite.html〕〔L.T. Morran; O.G. Schmidt; I.A. Gelarden; R.C. Parrish II; C.M. Lively. "Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex," Science, July 8, 2011. Document:Science.1206360. Indiana University.〕 Coevolution is primarily a biological concept, but researchers have applied it by analogy to fields such as computer science, sociology / international political economy and astronomy. ==Models== One model of coevolution was Leigh Van Valen's Red Queen's Hypothesis, which states that "for an evolutionary system, continuing development is needed just in order to maintain its fitness relative to the systems it is co-evolving with".〔Van Valen L. (1973): "A New Evolutionary Law", Evolutionary Theory 1, pp. 1–30. Cited in: (The Red Queen Principle )〕 This hypothesis predicts that sexual reproduction allows a host to stay just ahead of its parasite by a generation, similar to the Red Queen in "Through the Looking Glass". …always running ….. Just ahead. The essence is that the host reproduces sexually giving it immunity over its parasite, which then evolves in response. This requires the next generation to repeat the sequence.〔Sterns, S. (2009), Coevolution, EEB-122: Principles of evolution, ecology, and behavior, Open Yale Courses, retrieved from http://oyc.yale.edu/ecology-and-evolutionary-biology/eeb-122/lecture-20〕 Emphasizing the importance of sexual conflict, Thierry Lodé described the role of ''antagonist interactions'' in evolution, giving rise to a concept of ''antagonist coevolution''. Coevolution branching strategies for asexual population dynamics in limited resource environments have been modeled using the generalized Lotka–Volterra equations. A model based on adaptive dynamics and experimental data of floral and proboscis lengths, as well as nectar consumed and pollen deposited during the pollination of the long-tubed iris (''Lapeirousia anceps'') by the long-proboscid fly (''Moegistorhynchus longirostris'') has generated diverse coevolutionary dynamics, including two types of Red Queen dynamics, evolutionary branching (backed by observations of coexisting irises of short and long tubes in a single population) and trap. 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「Coevolution」の詳細全文を読む スポンサード リンク
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