The role of biotic interactions in determining phenotypic and genotypic variation in metal hyperaccumulation and hypertolerance in two model Brassicaceae species

金属超积累和金属超耐受性（mh）是十字花科植物的共同性状。然而，其生态后果和生态相互作用对自然性状变异的作用尚未得到研究。本文以两个遗传模式物种拟南芥（Arabidopsis halleri, Noccaea caerulescens）为研究对象，研究了该性状自然变异的原因和后果，并特别关注了植物与植物间负相互作用和正相互作用的作用。为此，我们结合了野外和温室研究、高端分子工具、数量遗传学和群落生态学实验方法。在第1阶段，我们研究了这个系统中存在竞争能力和抗逆性之间的权衡，影响了单个植物的性能，并决定了遗传和表型变异的程度。我们假设，在具有金属积累植物的种群和群落中，促进不同基因型在种群内共存，特别是在胁迫条件下，即在重金属含量高的土壤中。我们的现场结果和竞争实验的第一次测量为这一假设提供了初步的支持。在第二阶段，我们建议扩大我们的努力，在我们的两个模型物种中包括所有的积极和消极的相互作用。特别是，我们建议探索不同环境下植物-植物相互作用中mh的潜在差异结果，即植物修复引起的促进作用和植物富集引起的元素化感作用。此外，我们提出了研究合作相互作用的几个方面，其克隆繁殖可能在mh中发挥关键作用，并将其与第二种非克隆物种的模式进行比较。我们还将研究植物-食草动物相互作用及其对无性系植物和非无性系植物中mh水平的潜在影响。最后，我们将得到mh遗传力的估计。我们在两个项目阶段的总体发现将使我们能够评估自然栖息地生物相互作用中mh的表型和遗传变异的作用，反之亦然，以确定这种相互作用在驱动金属超积累和耐受性的种内和种间变异中的重要性。

Metal hyperaccumulation and metal hypertolerance (mh) are common traits in many Brassicaceae species. However, neither its ecological consequences nor the role of ecological interactions on natural trait variation have been studied. Here, we focus on two genetic model species (Arabidopsis halleri, Noccaea caerulescens) to study the causes and consequences of natural variation in this trait with a special focus on the role of negative and positive plant-plant interactions. To that end, we combine field and greenhouse studies, high-end molecular tools, quantitative genetics and experimental approaches of community ecology. In phase 1, we investigated the idea that a trade-off between competitive ability and stress tolerance exists in this system, affecting the performance of individual plants and determining the extent of genetic and phenotypic variation. We hypothesized that facilitation in populations and communities with metal accumulating plants will enable coexistence of different genotypes within the populations, especially under stressful conditions, i.e on soils with high content of heavy metals. Our field results and the first measurements from the competition experiments provide initial support for this hypothesis. In phase 2, we propose to expand our efforts to embrace the entire range of positive and negative interactions in our two model species. Particularly, we propose to explore the potentially contrasting outcomes of mh in plant-plant interactions under different environments, namely facilitation due to phytoremediation vs. elemental allelopathy due to phytoenrichment. Additionally, we propose to investigate several aspects of cooperative interactions in A. halleri, whose clonal propagation is likely to play a key role in mh, and we will contrast this with the patterns found in the second, non-clonal species. We will also investigate plant-herbivore interactions and their potential effect on mh levels within clonal vs. non-clonal plants. Finally, we will obtain estimates of heritability of mh in N. caerulescens. Our overall findings from both project phases will enable us to evaluate the role of phenotypic and genetic variation in mh for biotic interactions in natural habitats, and vice-versa, to determine the importance of such interactions in driving intra- and interspecific variation in metal hyperaccumulation and -tolerance.