Drought and parental effects shape plant responses to decreased precipitation predictability

Martí March-Salas, Lucrezia Laccetti, Linda Eberhardt, Charlotte Mundt, Vera Holland, Patrick S. Fitze, J F Scheepens

Current climate change is leading to an increase in the frequency and intensity of droughts and to decreased precipitation predictability, both potentially affecting the persistence of plant populations. Precipitation predictability has been shown to shape plant phenotypic variation and drive the evolution of phenotypic plasticity, yet whether differences in precipitation predictability also trigger parental environmental effects, and whether drought modifies their expression, remains unknown. To fill this gap, we performed a controlled greenhouse experiment on offspring of Papaver rhoeas L. (Papaveraceae) whose maternal lines had been exposed to more versus less predictable precipitation during three consecutive generations in an outdoor field experiment. Offspring were exposed to more or to less predictable precipitation, crossed with a control and a drought treatment, which allowed us to test whether offspring perform better under parental than under non-parental predictability regimes, and whether drought intensifies these responses. We measured growth-related (growth rate, total biomass), morphological (leaf length, specific root length) and physiological (chlorophyll content, photosynthetic performance) traits of the offspring. We found that contrasting levels of offspring precipitation predictability led to significant differences in growth rate, total biomass, leaf length and specific root length, whereas drought reduced plant growth independently of offspring predictability and modulated predictability effects on chlorophyll content. Offspring plants from the lower parental predictability treatment grew faster under less predictable compared to more predictable precipitation, indicating parental environmental effects on offspring growth responses. Overall, our study highlights that precipitation predictability is an important driver shaping plant phenotypic responses both within and across generations, and that its transgenerational effects are expressed mainly when both parents and offspring experience less predictable precipitation, while drought, which is expected to become increasingly frequent under climate change, can modulate these responses.