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.