1. Environmental conditions experienced by parent plants can influence offspring performance through parental effects induced by DNA methylation. The off spring can also be influenced by environmental conditions experienced by their parents via soil legacy effects due to plant-mediated changes in the composition of soil microbes. These two effects are likely to act simultaneously, but empirical evidence for combined effects is limited.
2. We conducted a two-phase experiment with five genotypes of a clonal plant Hydrocotyle vulgaris. In the first phase, we grew parent plants of each genotype under two light conditions (ambient vs. shade) and two DNA demethylation treatments [treated with water vs. 5-azacytidine (5-azaC)]. We then collected soils and clonal offspring for each genotype from each of these four treatments and measured soil (a)biotic properties. In the second phase, we grew the off spring from each of the four treatments in the four different soils, under the two light conditions.
3. When grown under ambient light condition and in soil from ambient parents, offspring produced by ambient parents grew larger than offspring produced by shaded parents when the parents were treated with water. This difference was smaller when the parents were treated with 5-azaC, and disappeared when the offspring were grown in soil from shaded parents. The growth difference was also observed when the offspring were grown under shaded condition and in soil from shaded parents. However, this difference was greater when the parents were treated with 5-azaC, and disappeared when the offspring were grown in soil from ambient parents. Moreover, offspring growth was associated with fungal composition and total phosphorus of the soil in which the parents had grown.
4. Our results show, for the first time, that light condition experienced by parents can influence offspring responses to light through both parental effects and soil legacies. The parental effects were mediated by changes in DNA methylation and the soil legacies were due to plant-mediated changes in a combination of soil biotic and abiotic properties. These impacts may eventually influence the ecological and evolutionary trajectories of clonal plant populations.