Joint impact of competition, summer precipitation, and maternal effects on survival and reproduction in the perennial Hieracium umbellatum

Are parental condition transfer effects more widespread than is currently appreciated?

It has long been recognized that the environment experienced by parents can influence the traits of offspring (i.e. 'parental effects'). Much research has explored whether mothers respond to predictable shifts in environmental signals by modifying offspring phenotypes to best match future conditions. Many organisms experience conditions that theory predicts should favor the evolution of such 'anticipatory parental effects', but such predictions have received limited empirical support. 'Condition transfer effects' are an alternative to anticipatory effects that occur when the environment experienced by parents during development influences offspring fitness. Condition transfer effects occur when parents that experience high-quality conditions produce offspring that exhibit higher fitness irrespective of the environmental conditions in the offspring generation. Condition transfer effects are not driven by external signals but are instead a byproduct of past environmental quality. They are also likely adaptive but have received far less attention than anticipatory effects. Here, we review the generality of condition transfer effects and show that they are much more widespread than is currently appreciated. Condition transfer effects are observed across taxa and are commonly associated with experimental manipulations of resource conditions experienced by parents. Our Review calls for increased research into condition transfer effects when considering the role of parental effects in ecology and evolution.

Effects of parental drought on offspring fitness vary among populations of a crop wild relative

Transgenerational plasticity is a form of non-genetic inheritance that can reduce or enhance offspring fitness depending on parental stress. Yet, the adaptive value of such parental environmental effects and whether their expression varies among populations remain largely unknown. We used self-fertilized lines from climatically distinct populations of the crop wild relative Lupinus angustifolius. In the parental generation, full-siblings were grown in two contrasting watering environments. Then, to robustly separate the within-generation and transgenerational response to drought, we reciprocally assigned the offspring of parents to the same experimental treatments. We measured key functional traits and assessed lifetime reproductive fitness. Offspring of drought-stressed parents produced less reproductive biomass, but a similar number of lighter seeds, in dry soil compared to offspring of genetically identical, well-watered parents, an effect not mediated by differences in seed provisioning. Importantly, while the offspring of parents grown in the favourable environment responded to drought by slightly increasing individual seed mass, the pattern of plasticity of the offspring of drought-grown parents showed the opposite direction, and the negative effects of parental drought on seed mass were more pronounced in populations from cooler and moist habitats. Overall, our results show that parental effects may override immediate adaptive responses to drought and provide evidence of population-level variation in the expression of transgenerational plasticity.