Evolutionary dynamics of quantitative variation in an adaptive trait at the regional scale: the case of zinc hyperaccumulation in Arabidopsis halleri

Metal hyperaccumulation in plants is an ecological trait whose biological significance remains debated, in particular because the selective pressures that govern its evolutionary dynamics are complex. One of the possible causes of quantitative variation in hyperaccumulation may be local adaptation to metalliferous soils. Here we explored the population genetic structure of Arabidopsis halleri at fourteen metalliferous and non-metalliferous sampling sites in Southern Poland. The results were integrated with a quantitative assessment of variation in zinc hyperaccumulation to trace local adaptation. We identified a clear hierarchical structure with two distinct genetic groups at the upper level of clustering. Interestingly, these groups corresponded to different geographic sub-regions, rather than to ecological types (i.e. metallicolous vs non-metallicolous). Also, approximate Bayesian computation analyses suggested that the current distribution of A. halleri in Southern Poland could be re...