Does phenotypic diversity induced by parental effects influence population structure and productivity?

Phenotypic diversity within a plant community can result from species diversity, genetic diversity and environmental variation. While phenotypic diversity mediated by species and genetic diversity can influence population structure and productivity, it is unclear whether phenotypic diversity induced by environmental variation can produce similar impacts. To test the hypothesis that phenotypic diversity mediated by environmental variation of parent plants can influence their offspring population structure and productivity via epigenetic modification, we conducted a two-phase experiment with the clonal plant Hydrocotyle verticillata . In the first phase, parent ramets derived from the same genotype were grown under eight different environmental conditions (2 light levels × 2 water levels × 2 nutrient levels) to produce offspring ramets of different phenotypes and were applied with a DNA demethylation agent (5-azacytidine) or not. In the second phase, we used the offspring ramets to construct populations containing one, three, or six phenotypes and grew them under the non-stressful condition. As expected, the parent ramets grown in the eight environmental conditions produced offspring ramets of different phenotypes, and such phenotypic variation was reduced by 5-azacytidine application. In contrast to our hypothesis, phenotypic diversity mediated by environmental variation of parents did not significantly affect population productivity (biomass) or population structure as measured by size variation of ramets. Also, this impact did not change by 5-azacytidine application. Therefore, our findings do not support the idea that phenotypic diversity mediated by parental effects can influence population structure and productivity via altering DNA methylation. The lack of sufficient niche differentiation among phenotypes and the absence of environmental stress may have limited the positive effects of phenotypic diversity on productivity. • Environment-induced phenotypic diversity may affect population characters. • Parental environmental variation induced offspring phenotypic diversity. • Offspring phenotypic diversity did not affect population productivity or structure. • DNA methylation played little role in this diversity effect.