“…This is consistent with the view that Arabidopsis populations in the west are the oldest, with later expansion into the eastern end of its native distribution, along with recently colonized regions, such as the Alps, in the center of the range (Sharbel et al, 2000;Nordborg et al, 2005;Schmid et al, 2005;Ostrowski et al, 2006;Beck et al, 2008;Picó et al, 2008;Platt et al, 2010;Cao et al, 2011). In addition, there is also altitudinal stratification within regions, with populations from high altitude being overall less diverse than those from lower altitude (Montesinos et al, 2009;Lewandowska-Sabat et al, 2010;Gomaa et al, 2011). It has also been suggested that there is evidence for migration from east to west, accompanying the spread of agriculture (François et al, 2008); however, knowing that the Iberian Peninsula is the most diverse region, it is unclear what to make from this.…”