Experimental test for adaptation to metalliferous soil. (a,b) Survival of A. halleri (a) and A. arenosa (b) plants originating from Mias (M site, red) and Zapa (NM site, black) transferred into metalliferous (Mias) or non-metalliferous (control) soil. (c,d) Fresh biomass of A. halleri (c) and A. arenosa (d) plants originating from Mias (M site, red) and Zapa (NM site, black) transferred into metalliferous (Mias) or non-metalliferous (control) soil. Shown are means and standard deviations of survival rate (a,b) and fresh above-ground biomass (c,d) after six weeks of cultivation on experimental soils (see the electronic supplementary material, table S4 for details).