Disruptive Selection

by

Adam M. Siepielski

• LAST REVIEWED: 25 November 2014
• LAST MODIFIED: 25 November 2014
• DOI: 10.1093/obo/9780199941728-0059

Introduction

A population experiences disruptive selection when more extreme phenotypes (or genotypes) within a population have a fitness advantage relative to intermediate forms. Disruptive selection has garnered much attention among evolutionary biologists and ecologists because of its role in the evolution and maintenance of phenotypic (and genetic) variation and speciation, particularly sympatric speciation. However, disruptive selection, by itself, is inherently thought to be unstable. This instability arises because, in the absence of frequency-dependence, one of the extreme phenotypes would be expected to have higher fitness than the other(s), which would cause disruptive selection to break down. Consequently, considerable theoretical work has focused on identifying the mechanisms that promote stable disruptive selection, while empirical work has centered on laboratory and field studies aimed at quantifying the occurrence, strength, and mechanisms driving disruptive selection. Recent reviews of empirical studies of selection in the wild have found that disruptive selection is surprisingly common and deserving of greater theoretical and empirical investigation.

Original Exposition

Darwin 1859 does not really distinguish among the different forms of selection (disruptive, directional, and stabilizing) currently recognized. It is unclear exactly when evolutionary biologists distinguished among these three main forms. Pearson 1903 deals with the effects of selection on the variances, covariances, and correlations between traits in a quantitative genetic treatment of the subject. The author does not refer to the forms of selection in this discourse; however, it is clear that he refers to disruptive selection. Wright 1932, a seminal paper on the adaptive landscape, provides a visual depiction of the relationship between fitness and genotypes, but does not distinguish among forms of selection. Simpson 1944, following Wright’s work (Wright 1932), clearly distinguishes among the different forms of selection in the two-trait case. However, this author too does not refer to them by their current names. Mather 1953 is perhaps the first to define the three currently recognized forms of selection.

• Darwin, C. 1859. On the origin of species by natural selection; or, The preservation of favored races in the struggle for life. London: John Murray.

  An impressive and exhaustive tour de force of comparative data outlining the basic mechanics of natural selection. Disruptive selection is not mentioned by name, but Darwin does discuss how competition could influence the dynamics of selection in a way consistent with modern views of density or frequency dependent selection driving disruptive selection.

• Mather, K. 1953. The genetical structure of populations. Symposia of the Society for Experimental Biology 7:66–95.

  In this paper Mather clearly distinguishes among the three forms of selection, including disruptive selection.

• Pearson, K. 1903. Mathematical contributions to the theory of evolution XI: On the influence of natural selection on the variability and correlation of organs. Philosophical Transactions of the Royal Society of London A 200:1–66.

  DOI: 10.1098/rsta.1903.0001

  In this paper Pearson outlines some of the basic statistical features of understanding selection in a quantitative genetics framework.

• Simpson, G. G. 1944. Tempo and Mode in Evolution. New York: Columbia Univ. Press.

  A foundational text in evolutionary biology in which Simpson briefly discusses different forms of selection.

• Wright, S. 1932. The roles of mutation, inbreeding, crossbreeding and selection in evolution. Proceedings of the 6th International Congress on Genetics 1:356–366.

  In this paper, Wright discusses variation in the form of selection, but did not distinguish among the forms of selection by their common vernacular.