The evolution of the G matrix: selection or drift?

Authors
Citation
D. Roff, The evolution of the G matrix: selection or drift?, HEREDITY, 84(2), 2000, pp. 135-142
Citations number
46
Language
INGLESE
art.tipo
Review
Categorie Soggetti
Biology,"Molecular Biology & Genetics
Journal title
HEREDITY
ISSN journal
0018-067X → ACNP
Volume
84
Issue
2
Year of publication
2000
Pages
135 - 142
Database
ISI
SICI code
0018-067X(200002)84:2<135:TEOTGM>2.0.ZU;2-X
Abstract
The evolution of quantitative characters can be described by the equation < Delta(z)over bar> = GP(-1)S where <Delta(z)over bar> is the vector of mean responses, G is the matrix of additive genetic variances and covariances, P is the matrix of phenotypic variances and covariances and S is the vector of selection differentials. This equation can be used to predict changes in trait values or to retrospectively estimate the selection gradient and is thus a central equation of evolutionary quantitative genetics. Genetic vari ances and covariances will be reduced by stabilizing selection, directional selection and drift, and increased by mutation. Changes in trait values re sulting from directional selection that are comparable with differences obs erved among species are readily obtainable in short geological time spans ( < 5000 generations) with selection intensities so small that they would hav e an insignificant effect on the G matrix (of course it is possible that su ch changes came about by strong selection over a few generations, followed by long periods of stasis; there is insufficient evidence to presently dist inguish these two possibilities). On the other hand, observed effective pop ulation sizes are sufficiently small that considerable changes in G can be expected from drift alone. The action of drift can be distinguished from se lection because the former produces a proportional change in G whereas the latter, in general, will not. A survey of studies examining variation in G suggests that the null hypothesis that most of the variation can be attribu ted to drift rather than selection cannot be rejected. However, more resear ch on the predicted statistical distribution of G as a result of selection and/or drift is required and further development of statistical tests to di stinguish these two forces needs to be made.