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，尤其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转移或增加的表型可塑性表现出快速的进化适应。第三种快速响应环境变化的机制是跨代可塑性（TGP），但研究较少。当亲代环境影响后代的表型和表现超出遗传基因的影响时，就会发生TGP。母体效应是TGP的一种特殊情况，当母体的环境影响到后代时，母体效应就会活跃起来。水分的可用性对植物的生长和发生具有决定性作用，并且在持续的气候变化下可能发生变化。然而，土壤水分条件变化对母系的影响尚未得到重视，大多数研究都是对单一一年生物种进行慢性、长期胁迫，主要是干旱胁迫。由于不仅是平均降水，极端降水事件的频率和强度也可能发生变化，因此有必要研究脉冲极端胁迫事件后的TGP，而不是慢性胁迫。该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，我们将重点研究土壤湿度长期变化（从非常潮湿、水饱和条件到长期干燥条件）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间的作用。此外，我们将确定竞争的强度和种类对后代表现的作用。本议程将对多个多年生物种进行研究，以估计母体效应的普遍程度，并得出哪些植物性状影响对母体效应的依赖的结论。由于已经进行了必要的母系处理，并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，因为我们可以在拟议的项目中直接开始抚养后代。我们主要检验以下假设：i)母亲的慢性压力会导致后代形态的压力类型特异性变化，从而导致后代在经历与母亲相同的压力时表现更好。ii)母亲的脉冲应激引起后代物候变化，当母亲和后代在一年中的同一时间出现应激脉冲时，后代的表现会更好。iii)在异交种中，母系效应较强，种子传播距离较短；iv)母系的地上竞争较强，子代在茎部生长上的投入较大；母系的地下竞争较强，子代在根系生长上的投入较大。

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.