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We have recently proposed new estimators of the parameters of genetic diversity and differentiation and of their variances for a haploid locus in a population subdivided into a large number of subpopulations, with a two-stage sampling of populations and individuals. Here they are compared with bootstrap estimators. Several resampling methods are evaluated: sampling of populations only, individuals within populations only, or both. Theoretical results and a numerical example show that the most appropriate bootstrap variance estimators are obtained by resampling the populations alone and not both populations and individuals. However, some bias is apparent in the bootstrap methods, and the direct estimators proposed previously should therefore be preferred.

Comparison of genetic differentiation in maritime pine ( Pinus pinaster Ait.) estimated using isozyme, total protein and terpenic loci

All species experience range expansions at some point in their history. Such episodes are typically short-lived; however, they can leave strong and persistent signatures in the genetic structure of the species. This realization came surprisingly late. In population genetics, ‘equilibrium' models had been designed to be independent of history, therefore ignoring episodes of range expansions. The first attempts to consider the historical settings when interpreting the genetic structure of populations were by geneticists with a strong naturalist background. For instance, the editors of the classic symposium volume The Genetics of Colonizing Species (Baker and Stebbins, 1965) were plant evolutionists with a particular interest in biogeography and palaeoecology. Their work predated by some 15 years the development of phylogeography in the early 1980s, which relied mostly on empirical methods. Quantitative approaches to study the genetics of colonization began later still. Although metapopulation models can be seen as representing a first step in this direction, they deal with local colonization balanced by extinctions, not pure expansions (Slatkin, 1977). The first quantitative studies of the genetic consequences of colonization of a new territory were published some 15–25 years ago and relied initially on simulations (Rendine et al., 1986; Nichols and Hewitt, 1994; Ibrahim et al., 1996), with analytical approaches following shortly after (Austerlitz et al., 1997; reviewed by Excoffier et al., 2009). Below, we consider one of these papers, published 14 years ago in Heredity (Ibrahim et al., 1996), which turned out to be particularly influential, with over 300 citations reported to date in ISI Web of Science, most of them after 2001.