Transgenerational plasticity affects fitness and mediates local adaptation

Transgenerational plasticity (TGP) could be as decisive of a factor in phenotypic outcomes as allelic variation and within-generation plasticity. While TGP is often associated with priming offspring to stress in stable environments (where offspring and grandparents are likely to experience similar stresses), our results suggest that TGP is locally adaptive for offspring when grandparents are exposed to environments that match historical conditions, regardless of the offspring’s environment. Specifically, we find that Mimulus cardinalis populations from historically wet environments exhibit adaptive TGP in grand-offspring, via increased male and female fitness, only when grandparents experience wet treatments, while TGP is maladaptive when these grandparents experience dry treatments. In contrast, populations from historically dry environments show the opposite. Furthermore, we find that TGP can have a greater effect on both male and female fitness than allelic differences and within-generation plasticity. Our results indicate an additional way that phenotypes arise through local adaption and sheds light on the potential for how rapid evolution might occur.