Transgenerational plasticity under environmental change: A multi-species study testing maternal effects of chronic dryness and wetness, of extreme pulsed stress and of competition change

在快速变化的环境条件下，特别是像植物这样的定居生物面临灭绝的危险。为了生存，它们必须通过等位基因频率变化或增加表型可塑性来显示快速的进化适应。第三种对环境变化做出快速反应的机制是跨代可塑性（transgenerational plasticity，TGP），这种机制的研究较少。作为三峡工程的一个特殊情况，当母体环境影响后代时，母体效应是活跃的。水分供应对植物生长和发生具有决定性作用，并可能在持续的气候变化下发生变化。然而，母亲的影响，土壤水分条件的变化，并没有得到太多的关注，大多数研究应用慢性，持久的压力，主要是干燥，对单一的一年生物种。由于不仅平均降水量，而且极端降水事件的频率和强度都可能发生变化，因此有必要研究三峡工程在脉冲极端应力事件后与慢性应力相比的变化。拟议项目的总体目标是阐明慢性与脉冲非生物应激和生物应激（竞争）对后代表现的母体影响。在田间试验中，我们将重点研究从非常潮湿、水饱和条件到长期干旱条件下土壤水分长期变化下的跨代可塑性。我们将进一步测试极端压力脉冲对母体的影响，特别关注这种压力脉冲的时机的作用。此外，我们将确定竞争的强度和种类对后代的表现的作用。这一议程将与多个，多年生物种进行估计母体效应的患病率，并得出结论，哪些植物性状影响对母体效应的依赖。由于已经进行了必要的母体治疗，并且已经在现有项目的框架内收集了种子，我们有独特的机会与多年生植物合作，因为我们可以直接在拟议的项目中开始饲养后代。我们主要检验以下假设：（1）母亲的慢性压力会导致后代形态学上的压力类型特异性变化，当后代经历与母亲相同的压力时，这些变化会导致表现改善。ii）母亲的脉冲压力导致后代物候的变化，当母亲和后代压力脉冲在一年中的同一时间发生时，这导致后代表现更好。（3）在种子传播距离较短的异交种中，母体的作用更强。（4）母体经历的强烈的地上竞争导致后代在地上部生长中更大的投资，而在后代根部生长中，母体经历的强烈的地下竞争导致后代在地上部生长中更大的投资。

Under rapidly changing environmental conditions, especially sedentary organisms like plants are at the risk of extinction. To survive they must show rapid evolutionary adaptation via allele frequency shifts or increased phenotypic plasticity. A third, but less well investigated mechanism for rapidly responding to environmental change is transgenerational plasticity (TGP).TGP occurs when the parental environment affects offspring phenotype and performance beyond the effects of transmitted genes. Maternal effects, a special case of TGP, are active when the environment of the mother affects offspring.Water availability is decisive for plant growth and occurrence and likely to change under ongoing climate change. Maternal effects of changed soil moisture conditions, however, have not received much attention and most studies applied chronic, long lasting stress, mainly dryness, on single annual species. As not only average precipitation, but also frequency and intensity of extreme precipitation events are likely to change, it is necessary to investigate TGP after pulsed, extreme stress events, in contrast to chronic stress. The overall aim of the proposed project is to elucidate maternal effects of chronic versus pulsed abiotic stress and of biotic stress (competition) on offspring performance. In a field experiment, we will focus on transgenerational plasticity under chronically changed soil moisture ranging from very wet, water saturated conditions to chronically dry conditions. We will further test for maternal effects of extreme stress pulses, with a special focus on the role of timing of such stress pulses. Furthermore, we will determine the role of intensity and kind of competition on offspring performance. This agenda will be conducted with multiple, perennial species to estimate the prevalence of maternal effects and to draw conclusions on which plant traits affect the reliance on maternal effects. As the necessary maternal treatments have already been conducted and seeds have been collected in the frame of an existing project, we have the unique opportunity to work with perennials because we can directly start with raising the offspring in the proposed project. We mainly test the following hypotheses: i) Chronic stress for mothers causes stress-type specific changes in offspring morphology that lead to improved performance when offspring experience the same stress as mothers. ii) Pulsed stress for mothers causes changes in offspring phenology that lead to better performance of offspring when maternal and offspring stress pulse occur at the same time of the year. iii) Maternal effects are stronger in outcrossing species with short distance seed dispersal iv) Strong aboveground competition experienced by mothers causes greater offspring investment in shoot growth, strong maternal belowground competition in offspring root growth.