Trans-generational effects in the clonal invader Alternanthera philoxeroides.
Aims: Recent studies have revealed heritable phenotypic plasticity through vegetative generations. In this sense, changes in gene regulation induced by the environment, such as DNA methylation (i.e. epigenetic changes), can result in reversible plastic responses being transferred to the offspring generations. This trans-generational plasticity is expected to be especially relevant in clonal plants, since reduction of sexual reproduction can decrease the potential for adaptation through genetic variation. Many of the most aggressive plant invaders are clonal, and clonality has been suggested as key to explain plant invasiveness. Here we aim to determine whether trans-generational effects occur in the clonal invader Alternanthera philoxeroides, and whether such effects differ between populations from native and non-native ranges. Methods: In a common garden experiment, parent plants of A. philoxeroides from populations collected in Brazil (native range) and Iberian Peninsula (non-native range) were grown in high and low soil nutrient conditions, and offspring plants were transplanted to control conditions with high nutrients. To test the potential role of DNA methylation on trans-generational plasticity, half of the parent plants were treated with the demethylating agent, 5-azacytidine. Important Findings: Trans-generational effects were observed both in populations from the native and the non-native ranges. Interestingly, trans-generational effects occurred on growth variables (number of ramets, stem mass, root mass and total mass) in the population from the native range, but on biomass partitioning in the population from the non-native range. Trans-generational effects of the population from the native range may be explained by a 'silver-spoon' effect, whereas those of the population from the non-native range could be explained by epigenetic transmission due to DNA methylation. Our study highlights the importance of trans-generational effects on the growth of a clonal plant, which could help to understand the mechanisms underlying expansion success of many clonal plants.