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

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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.