8. bradshaw and colleagues found that grasses growing in copper mine tailings had evolved an increased tolerance of heavy metals. this trait was confined to the local population on tailings for all of the following reasons except: a. seeds from grasses in toxic soils killed all seed dispersers, preventing germination of tolerant grasses off the tailings. b. grasses in toxic soils flowered earlier, with increased rates of selfing compared to grasses in normal soils, thus decreasing gene flow c. in toxic soils, grasses without the tolerant trait survived and reproduced less well d. in normal soils, grasses without the tolerant trait outcompeted grasses with the trait