Phenotypic plasticity accounts for most of the variation in leaf manganese concentrations in Phytolacca americana growing in manganese-contaminated environments

Abstract

Phytolacca americana, a globally invasive species, is able to flourish in heavy metal-contaminated habitats. To improve understanding of the adaptive evolutionary mechanisms of plants under heavy metal stress, we investigated key factors contributing to variation in leaf manganese (Mn) content in P. americana. Genetic surveys and common garden experiments were conducted simultaneously in an analysis of P. americana populations growing on Mn-contaminated and uncontaminated soil. Our field survey detected a significant relationship between leaf Mn concentrations in P. americana and concentrations in the soils from which plants were collected. Microsatellite analyses identified low levels of genetic diversity within and between populations; 32 of 39 populations (82 %) were genetically monomorphic. No genetic differentiation was detected between populations from contaminated and uncontaminated soils. Our common garden experiments showed that Mn concentrations in P. americana were related only to the growth habitat, regardless of the origin of the seeds. Combining the results of our ecological and genetic analyses, we concluded that genetic variation is not likely to be responsible for the wide ecological distribution of P. americana in China. Rather, phenotypic plasticity is probably the major contributor to its successful colonisation of stressful habitats, such as heavy metal-contaminated soils.