Natural Genetic Variation of Arabidopsis thaliana is Geographically Structured in the Iberian Peninsula

To understand the demographical history of Arabidopsis thaliana within its native geographic range, we have studied its genetic structure in the Iberian Peninsula region. We have analysed the amount and spatial distribution of A. thaliana genetic variation by genotyping 268 individuals sampled in 100 natural populations from the Iberian Peninsula. Analyses of 175 individuals from seven of these populations, with 20 chloroplast and nuclear microsatellite loci and 109 common single nucleotide polymorphisms, show significant population differentiation and isolation by distance. In addition, analyses of one genotype from 100 populations detected significant isolation by distance over the entire Peninsula, as well as among six Iberian subregions. Analyses of these 100 genotypes with different model-based clustering algorithms inferred four genetic clusters, which show a clear cut geographical differentiation pattern. On the other hand, clustering analysis of a world-wide sample showed a west-east Eurasian longitudinal spatial gradient of the commonest Iberian genetic cluster. These results indicate that A. thaliana genetic variation displays significant regional structure, and consistently support the hypothesis that Iberia has been a glacial refugium for A. thaliana. In addition, the Iberian geographical structure indicates a complex regional population dynamics, suggesting that this region contained multiple Pleistocene refugia with different contribution to the postglacial colonization of Europe.

Key Words: Arabidopsis, genetic structure, genome-wide analysis, isolation by distance, natural variation

Online ISS 1091-6490
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