3.1 Heavy metal levels and morphology of S. cataractae from the field
The concentrations of Cd and Cu in soils (total levels) differed significantly across sites (χ² = 0.64, p < 2.2e-16 and χ² = 4.36, p < 2.2e-16 for Cd and Cu respectively; Figure 1). Site 2 (in the center of the mine) showed the highest concentrations of Cu, followed by sites 1 (edge) and 3 (center), and ultimately 4 (edge). For Cd, site 3 showed the highest concentration followed by sites 2, 1 and 4 (which did not differ from each other). Total levels of Cd and Cu inS. cataractae also differed among populations (χ² = 3.00, p<0.0001 and χ² = 1.28, p<0.001 for Cd and Cu respectively), however, the differences found in plants did not reflect the same pattern as found in soils. Total and relative Cu were highest in Sc3 and did not differ significantly among the other three populations (Fig. 1B and 1C). Total Cd was lowest in Sc1 and did not differ significantly among the other three populations (Fig. 1D). The relative levels of Cd in plant tissue, however, did not show significant differences among populations (χ² = 0.02, p=0.615; Fig. 1F).
The morphological measurements performed on the field samples revealed that plants from the center of the mine (Sc2, Sc3) were smaller than those from the edges (Sc1, Sc4) for all traits studied except leaf width in Sc2 (χ² = 24.80, p < 2.2e-16 for plant length; χ² = 2.75, p < 2.2e-16 for leaf length; χ² = 3.39, p < 2.2e-16 for leaf width; Fig. 1G to I).