A model of the migration pattern in a metapopulation of sea beet (
on the continuous distributions of seed and pollen movements, is fitted to gene frequency data at 12
isozyme and RFLP loci by maximum likelihood by using an approximation of the simultaneous equilibrium
distribution of the gene frequencies generated by the underlying multivariate stochastic process of genetic
drift in the population. Several alternative restrictions of the general model are fitted to the data, including
the island model, a model of complete isolation, and a model in which the seed and pollen dispersal
variances are equal. Several likelihood ratio tests between these alternatives are performed, and median
bias in the estimated parameters is corrected by using parametric bootstrapping. To assess the fit of the
selected model, the predicted covariances are compared with covariances computed from the data directly.
The dependency of estimated parameters on the ratio between effective and absolute subpopulation sizes,
which is treated as a known parameter in the analysis, is also examined. Finally, we note that the data
also appear to contain some information about this ratio.