Format: ORAL

Mar Sobral1 Francesco de Bello2

1. University of Santiago de Compostela, Santiago de Compostela, Spain. 2. CIDE, CSIC, Valencia, Spain.

Non-genetic heritable variances in phenotype, within and across populations, play a crucial role in facilitating adaptation in non-mobile organisms like plants. They regulate the expression of traits in response to shifts in the environment. In addition to within-generation plasticity (short-term modifications occurring within an individuals lifetime), plasticity can be inherited across generations, manifesting as non-genetic effects shaped by the conditions in which parental plants developed (transgenerational plasticity). The extent to which these non-genetic effects accumulate in stable environmental conditions and how rapidly they revert when conditions change remains unclear. In a three-generation experiment with wild radish, we maintained different cohorts in either consistent or varied environmental conditions, with respect to the conditions experienced by parental generations, with or without herbivory by caterpillars. Results revealed a robust plastic response marked by phenotypic adaptation, specifically an increase in plant defenses characterized by two traitstrichome abundance and glucosinolate production. As expected, conditions experienced during a plants lifetime induce a strong plastic response within an organisms life cycle. However, our findings also demonstrate that transgenerational plasticity cumulatively reinforces lifetime plasticity, particularly for individuals whose all previous parental generations were grown in the same conditions. This cumulative effect causes phenotypes of a given genotype to diverge when exposed for several generations to either stressed or benign conditions, resulting in increased non-genetic phenotypic divergence across populations grown for several generations in different environments. Contrarily, in more unstable environments, where conditions varied across parental generations, we observed increased phenotypic differences among individuals growing in the same conditions. This suggests the presence of mechanisms supporting bet-hedging effectsenhanced trait diversity to potentially bolster population resilience. These results highlight important and previously unexplored effects with implications for ecological theories beyond species adaptation.