Copper tolerance testing in populations of Mimulus luteus var. variegatus exposed and non-exposed to copper mine pollution

Abstract

Several plant species have evolved metal tolerance as a response to increasing metal concentration in soils due to human activities. A well-described example is the evolution of copper-tolerant ecotypes of the monkey flower ( Mimulus guttatus ) in Copperopolis, California. Although copper mine activities have been intense in some areas of the Andes Range in central Chile, metal-tolerant ecotypes have not been reported for any native or endemic plant species. Copper tolerance of two populations of Mimulus luteus var. variegatus from pristine basins (Río Cipreses and Las Cayanas) and one population from a highly polluted copper mine area (Sewell) were tested to determine their copper tolerance. Tolerance was tested on cuttings collected in the field from adult plants (Sewell population) and on cuttings from plants cultivated from seeds in the laboratory (Río Cipreses, Las Cayanas and Sewell). All cuttings were grown under increasing concentrations of copper (0, 0.5 and 2.0 mg l −1 ) in calcium nitrate (0.5 g l −1 ). Results indicated that root number and length were strongly inhibited in M. luteus var. variegatus from Río Cipreses and Las Cayanas, but tolerant individuals were found in the Sewell population. The degree of copper tolerance of M. luteus var. variegatus from Sewell was, however, lower than that of individuals of Mimulus guttatus from Copperopolis.