What statistical methods are presently available to test for variation among G matrices?
Given the G matrix of two or more populations consisting of either the same or different species we are in the first instance interested in two questions: first, ‘can we reject the hypothesis that the matrices came from the same statistical population?’. This null hypothesis supposes that the populations do not differ in population size, selection history or mutational variances. We might be inclined to entertain such a hypothesis when comparing several populations of the same species but it seems an unlikely scenario when considering different species. The second question is, ‘can we reject the hypothesis that differences among the G matrices can be accounted for on the basis of drift alone?’ This hypothesis does not preclude the possibility that there are differences in selection history or mutational variances among the populations, but postulates that genetic drift will be relatively so large that it overwhelms such effects. It is important to remember that proportionality of the G
