How does the environment of parents or grandparents affect offspring? The importance of transgenerational plasticity is becoming more understood, but whether different populations are predisposed to express transgenerational plasticity and whether this assists or hinders rapid adaptation to environmental change is little understood. We used a recent unprecedented drought (2011-2016) in the western USA as a case study of a major selective force for adaptation in scarlet monkeyflower (Mimulus cardinalis) to ask 1) whether different populations are more likely to exhibit transgenerational plasticity based on historical climate?; and 2) does transgenerational plasticity change following drought? To answer these questions we used a resurrection approach, where ancestral (pre-drought) and descendant (peak-drought) plants are grown in a common environment. We grew plants from regions with distinct climatic histories: the north with low interannual variability and higher precipitation and the south with high interannual variability and low precipitation. Plants were grown for three generations under wet or dry treatments, resulting in four treatment history categories. We compared life history traits (germination and flowering date), as well as growth indices (such as specific leaf area and biomass).
Results/Conclusions
Overall northern populations exhibited greater plasticity as a result of their grandparental and parental environments compared to southern populations. Plants from northern environments flowered earliest and had thicker leaves after two generations of dry treatments and flowered later with thinner leaves following two generations of wet treatments, whereas there was no clear effect for either of these traits in the south. Germination time was unaffected when the two previous generations had the same environment but was significantly different when environments changed. Seeds from dry grandparent followed by wet parent had later germination time, whereas wet grandparent followed by dry parent had earlier germination time. Both regions had greater biomass when either the grandparent or parent had been exposed to a dry treatment, with two generations of dry being the heaviest. These results suggest that climatically stable environments (north) result in greater expression of transgenerational plasticity perhaps because grandparent environments are more likely to reflect grand-offspring environments. Additionally, we found no evidence that this relationship changed overtime, suggesting that it does not evolve rapidly. The expression of transgenerational plasticity may provide insight into how populations respond rapidly with consistent change but also why there are phenotypic lags following climatic perturbations.
