|
Stabilizing selection (not the same thing as negative selection〔http://www.nature.com/scitable/topicpage/Negative-Selection-1136〕) is a type of natural selection in which genetic diversity decreases and the population mean stabilizes on a particular trait value. This is thought to be the most common mechanism of action for natural selection because most traits do not appear to change drastically over time. 〔Charlesworth B, Lande R, Slatkin M (1982) "A neo-Darwinian commentary on macroevolution." ''Evolution'' 36-3 http://www.jstor.org/discover/10.2307/2408095?uid=3739448&uid=2131&uid=2&uid=70&uid=3737720&uid=4&sid=21102032998907〕 Stabilizing selection commonly uses negative selection (a.k.a. purifying selection) to select against extreme values of the character. Stabilizing selection is the opposite of disruptive selection. Instead of favoring individuals with extreme phenotypes, it favors the intermediate variants. It reduces phenotypic variation and maintains the status quo. Natural selection tends to remove the more severe phenotypes, resulting in the reproductive success of the norm or average phenotypes. For example, the African butterfly ''Bicyclus anynana'' exhibits stabilizing selection with its wing eyespots.〔Brakefield, Paul M., Patrícia Beldade, and Bas J. Zwaan. "The African butterfly ''Bicyclus anynana'': a model for evolutionary genetics and evolutionary developmental biology." Cold Spring Harbor Protocols 2009.5 (2009): pdb-emo122.〕 A classic example of this is human birth weight. Babies of low weight lose heat more quickly and get ill from infectious diseases more easily, whereas babies of large body weight are more difficult to deliver through the pelvis. Infants of a more medium weight survive much more often. For the larger or smaller babies, the baby mortality rate is much higher. Because most traits change little over time, stabilizing selection is thought to be the most common type of selection in most populations. 〔Charlesworth B, Lande R, Slatkin M (1982) "A neo-Darwinian commentary on macro-evolution." ''Evolution'' 36-3 http://www.jstor.org/discover/10.2307/2408095?uid=3739448&uid=2131&uid=2&uid=70&uid=3737720&uid=4&sid=21102032998907〕 However, a meta-analysis of studies that measured selection in the wild failed to find an overall trend for stabilizing selection. 〔Kingsolver JG, Hoekstra HE, Hoekstra J, Berrigan D, Vignieri SN, Hill CE, Hoang A, Gilbert P, Beerli P. (2001) "The Strength of Super Genetic Selection in Natural Populations." ''The American Naturalist'' 157-3 http://www.oeb.harvard.edu/faculty/hoekstra/pdfs/kingsolver2001amnat.pdf 〕 The reason can be that methods for detecting stabilizing selection are complex. They can involve studying the changes that causes natural selection in the mean and variance of the trait, or measuring fitness for a range of different phenotypes under natural conditions and examining the relationship between these fitness measurements and the trait value, but analysis and interpretation of the results is not straightforward. 〔Lande R and Arnold SJ. (1983) "The Measurement of Selection on Correlated Characters." ''Evolution'' 37-6 〕 ==See also== *Balancing selection *Koinophilia *Directional selection *Frequency-dependent foraging by pollinators *Assortative mating *Hypergamy 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「Stabilizing selection」の詳細全文を読む スポンサード リンク
|