Genetic variability in natural populations of Arabidopsis thaliana in northern Europe

Abstract

Ten populations of the model plant Arabidopsis thaliana were collected along a north-south gradient in Norway and screened for microsatellite polymorphisms in 25 loci and variability in quantitative traits. Overall, the average levels of genetic diversity were found to be relatively high in these populations, compared to previously published surveys of within population variability. Six of the populations were polymorphic at microsatellite loci, resulting in an overall proportion of polymorphic loci of 18%, and a relatively high gene diversity for a selfing species (HE = 0.06). Of the overall variability, 12% was found within populations. Two of six polymorphic populations contained heterozygous individuals. Both FST and phylogenetic analyses showed no correlation between geographical and genetic distances. Haplotypic diversity patterns suggested postglacial colonization of Scandinavia from a number of different sources. Heritable variation was observed for many of the studied quantitative traits, with all populations showing variability in at least some traits, even populations with no microsatellite variability. There was a positive association between variability in quantitative traits and microsatellites within populations. Several quantitative traits exhibited QST values significantly less than FST, suggesting that selection may be acting to retard differentiation for these traits.

Natural Genetic Variation ofArabidopsis thalianaIs Geographically Structured in the Iberian Peninsula

“…In agreement with previous studies (Stenøien et al 2005;Bakker et al 2006), several results indicate that migration, outcrossing, and de novo mutation differentially contribute to the variation within populations. First, chloroplast and nuclear haplotype analyses show that most populations contain not only related but also genetically unrelated individuals (supplemental Figure S4), suggesting that seed migration is an important factor contributing to within-population diversity.…”

“…In agreement, a large variation among populations was also found for outcrossing rate estimates. Iberian populations presented an average outcrossing frequency of 2.5%, which is slightly larger than previous MS-based estimates (Le Corre 2005;Stenøien et al 2005;Bakker et al 2006). This is probably due to the larger diversity of Iberian populations and not to mistyping errors because the three main sources of MS scoring errors (stutter bands, large-allele dropout, and null alleles) lead to underestimations of heterozygosity (reviewed in Dewoody et al 2006).…”

“…Average F ST values indicate that 66% of the genetic variation is segregating within these populations. Different proportions of within-population diversity have been found in other world regions, ranging from 77 to 36% in North America (Bergelson et al 1998;Jørgensen and Mauricio 2004), 57% in Europe (Bakker et al 2006), 54% in China (He et al 2007), 41% in France (Le Corre 2005, 12% in Norway (Stenøien et al 2005), and 0% in Japan (Todokoro et al 1995). In agreement with Beck et al (2008), the large fraction of genetic variation segregating within Iberian populations at MS and SNP loci suggests a south-north latitudinal gradient of local population diversity in Europe.…”

“…Thus far, a significant regional correlation between genetic and geographical distances has been observed only in China, which supports a progressive natural dispersal under strong anthropogenic influence. In contrast, lack of such correlations within non-native regions has been interpreted as a consequence of a recent colonization and expansion from mixed origin or a consequence of 1 multiple colonizations (Todokoroet al 1996;Jørgensen and Mauricio 2004;Stenøien et al 2005).…”

“…These analyses have found significant population structure on a global scale, as well as long-range isolation by distance among different world regions (Sharbel et al 2000;Nordborg et al 2005;Ostrowski et al 2006;Schmid et al 2006;Beck et al 2008). In addition, several laboratories have recently initiated the development of new A. thaliana collections for genetic variation studies on a regional scale in regions of the native distribution area such as northern Europe (Stenøien et al 2005;Bakker et al 2006), France (Le Corre 2005), central Asia (Schmid et al 2006), and China (He et al 2007), as well as in regions of presumed recent introduction and expansion such as Japan (Todokoro et al 1996) and North America ( Jørgensen and Mauricio 2004;Bakker et al 2006). Thus far, a significant regional correlation between genetic and geographical distances has been observed only in China, which supports a progressive natural dispersal under strong anthropogenic influence.…”