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Ecological fitting
Ecological fitting is "the process whereby organisms colonize and persist in novel environments, use novel resources or form novel associations with other species as a result of the suites of traits that they carry at the time they encounter the novel condition.”
It can be understood as a situation in which a species' interactions with its biotic and abiotic environment seem to indicate a history of coevolution, when in actuality the relevant traits evolved in response to a different set of biotic and abiotic conditions.〔 The simplest form of ecological fitting is resource tracking, in which an organism continues to exploit the same resources, but in a new host or environment. In this framework, the organism occupies a multidimensional operative environment defined by the conditions in which it can persist, similar to the idea of the Hutchinsonian niche. In this case, a species can colonize new environments (e.g. an area with the same temperature and water regime) and/or form new species interactions (e.g. a parasite infecting a new host) which can lead to the misinterpretation of the relationship as coevolution, although the organism has not evolved and is continuing to exploit the same resources it always has.〔 The more strict definition of ecological fitting requires that a species encounter an environment or host outside of its original operative environment and obtain realized fitness based on traits developed in previous environments that are now co-opted for a new purpose. This strict form of ecological fitting can also be expressed either as colonization of new habitat or the formation of new species interactions.〔
== Origin ==
The evolutionary ecologist Dr. Daniel Janzen began to explicate the idea of ecological fitting with a 1980 paper that observed that many instances of ecological interactions were inferred to be the result of coevolution when this was not necessarily the case, and encouraged ecologists to use the term coevolution more strictly. He observed that the existing defense traits of plants were likely produced by co-evolution with herbivores or parasites that no longer co-occurred with the plants, but that these traits were continuing to protect the plants against new attacks.
He expanded this idea in a 1985 paper written while visiting Santa Rosa National Park in Costa Rica. While there, he observed that almost all of the species in the park occupied large geographic ranges, and despite the heterogeneity of habitats across these ranges, individuals were mostly identical across locations, indicating that little local adaptation had taken place. He described the cyclical life history pattern he believed responsible for this pattern: a species begins as a small population occupying a small area with little genetic variation, but then over the course of a few generations grows to occupy a large area, either because of the emergence of a genotype successful over a wider range, or because of the removal of a geographic barrier. This large interconnected population is now subject to many contradictory selection pressures and thus remains evolutionarily static until a disturbance separates populations, restarting the cycle.〔 This cyclic life history pattern is dependent on three premises: that the ancestral range of most species is smaller than the ones now occupied, that biological communities have porous borders and are thus subject to invasion, and that species possess robust genotypes that allow them to colonize new habitats without evolution.〔 Thus, many biological communities may be made up of organisms that despite their complex biological interactions have very little evolutionary history with each other.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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