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Prey switching is frequency-dependent predation, where the predator preferentially consumes the most common type of prey. The phenomenon has also been described as apostatic selection, however the two terms are generally used to describe different parts of the same phenomenon. Apostatic selection has been used by authors looking at the differences between different genetic morphs. In comparison, prey switching has been used when describing the choice between different species.〔Allen, J.A. (1988) Frequency-dependent selection by predators. Philos. T. Roy. Soc. B 319, 485-503〕 ==Definition== The term ''switching'' was first coined by the ecologist Murdoch in 1969 to describe the situation where a predator eats disproportionately more of the most common type of prey.〔Murdoch,W.W. (1969) Switching in generalist predators: experiments on prey specificity and stability of prey populations. Ecol. Monogr. 39, 335–354〕 Eight years earlier in 1962 the geneticst B. C. Clarke described a similar phenomenon and called it "apostatic selection".〔Clarke, B.C. (1962) Balanced polymorphism and the diversity of sympatric species. In Taxonomy and Geography (Nichols, D., ed), pp. 47-70, Oxford: Systematics Association Publication〕 Since then the term ''prey switching'' has mainly been used by ecologists, while ''apostatic selection'' has been used by geneticists, and because of this they have been used to describe different aspects of frequency dependent selection. One of the ways prey switching has been identified and defined is when a predator's preference for a particular type of prey increases as the prey increase in abundance. The result is a strong preference for prey which are common in the environment and a weak preference for prey which are rare. The definition of preference will therefore impact on understanding switching. The most common definition of preference is the relationship between the ratio of prey in the environment and the ratio of prey in a predator's diet. It has been independently proposed a number of times and is described by the equation: ::P1/P2 = c (N1/N2); alternatively, c = (P1/P2)/(N1/N2) where ''N1'' and ''N2'' are the abundance of prey types 1 and 2 in the environment and ''P1'' and ''P2'' are the abundances of the same prey types in the predator's diet. ''c'' is the preference for prey type 1. If the value of ''c'' increases over time with ''N1/N2'', prey switching is presumed to occur. The opposite of prey switching is when a predator eats disproportionately more of the most rare prey than would be expected by chance. From the equation above this would occur when ''c'' (preference) decreases over time as ''N1''/''N2'' (amount in the environment) increases. This opposite phenomenon has been called negative prey switching, or anti-apostatic selection when it refers to the choice between different morphs. Prey switching has been in the scientific literature for around 40 years, but since his initial work Hassell has suggested that interest in prey switching has fallen since it is hard to demonstrate whether it has or is occurring.〔Hassell, M.P. (2000) The Spatial and Temporal Dynamics of Host Parasitoid Interactions, Oxford University Press〕 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「Prey switching」の詳細全文を読む スポンサード リンク
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