Data from: Rapid transgenerational effects in Knautia arvensis in response to plant-community diversity

1. Plant-species persistence in natural communities requires coping with biotic and abiotic challenges. These challenges also depend on plant-community composition and diversity. Over time, biodiversity effects have been shown to be strengthened via increasing species complementarity in mixtures. Little is known, however, whether differences in community diversity and composition induce rapid transgenerational phenotypic adaptive differentiation during community assembly. We expect, altered plant-plant and other biotic interactions (mutualists or antagonists) in high vs. low diverse communities to affect immediate within- and between species-trait differentiations due to competition for light and nutrients. 2. Three years after the initiation of a large-scale, long-term biodiversity experiment in Jena, Germany, we tested for effects of varying experimental plant-community diversity (1–60 plant species; 1–4 plant functional groups) and composition (with or without legumes and/or grasses) on phenotypic differentiation and variation of the tall herb Knautia arvensis. We measured reproduction at different diversity levels in the Jena experiment (residents hereafter) and, in an additional common garden experiment without competition, recorded subsequent offspring performance (i.e., growth, reproductive success and susceptibility to powdery mildew) to test for differentiation in phenotypic expression and variability. 3. We observed phenotypic differences among diversity levels with reduced fecundity of K. arvensis residents in more diverse communities. In the next generation grown under common garden conditions, offspring from high diversity plots showed reduced growth (i.e., height) and lower reproduction (i.e., fewer infructescences), but increased phenotypic trait variability (e.g., in leaf width and powdery mildew presence) and also tended to be less susceptible to powdery mildew infection. 4. Community composition also affected Knautia parents and offspring. In the presence of legumes resident plants produced more seeds (increased fecundity), however germination rate of those seeds was reduced at an early seedling stage (reduced fertility). 5. Synthesis: We conclude that rapid transgenerational effects of community diversity and composition on both mean and variation of phenotypic traits among offspring exist. Additional to heritable variation, environmentally induced epigenetic and/ or maternal processes matter for early plant community assembly and may also determine future species co-existence and community stability.

1. 自然群落中的植物物种存续（plant-species persistence）需要应对生物与非生物胁迫（biotic and abiotic challenges）。这类胁迫同样取决于植物群落组成（plant-community composition）与多样性。既往研究表明，群落内物种间生态位互补性（species complementarity）的增强会强化生物多样性效应。然而，目前学界对群落多样性与组成的差异是否会在群落组装（community assembly）过程中引发快速的跨代表型适应性分化（transgenerational phenotypic adaptive differentiation）仍知之甚少。我们推测，相较于低多样性群落，高多样性群落中植物间及其他生物互作（共生者或拮抗者，mutualists or antagonists）的改变，会通过光与养分的竞争，直接影响物种种内与种间的性状分化（trait differentiations）。
2. 在德国开展的大规模长期生物多样性实验——耶拿实验（Jena Experiment）启动三年后，我们针对不同实验植物群落多样性（1~60种植物；1~4个植物功能群（plant functional groups））与组成（是否包含豆科植物（legumes）和/或草本植物（grasses））对高大草本植物山萝卜（Knautia arvensis）的表型分化与变异的影响展开了测试。我们在耶拿实验中测定了不同多样性水平下本土植株（后文简称“本土植株”）的繁殖情况，并在另一项无竞争的同质园实验（common garden experiment）中记录了后续子代的表现（即生长状况、繁殖成功率与白粉病（powdery mildew）易感性），以此检验表型表达与变异的分化情况。
3. 我们观察到不同多样性水平下存在表型差异：在更高多样性的群落中，山萝卜本土植株的结实率（fecundity）有所降低。在同质园条件下培育的下一代中，来自高多样性样地的子代植株生长受到抑制（即株高更低）、繁殖能力下降（即果序（infructescences）数量更少），但表型性状的变异程度更高（例如叶宽与白粉病感染情况），且对白粉病感染的易感性也有所降低。
4. 群落组成同样会影响山萝卜的亲本与子代植株。当群落中存在豆科植物时，本土植株的结籽量更高（结实率提升），但这类种子在幼苗早期的发芽率却有所降低（育性下降）。
5. 综合分析：我们得出结论，群落多样性与组成对子代表型性状的均值与变异均存在快速跨代效应。除可遗传变异之外，环境诱导的表观遗传（epigenetic）和/或母体效应过程对于早期植物群落组装至关重要，同时也可能决定未来的物种共存（species co-existence）与群落稳定性（community stability）。