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性是许多十字花科植物的共同特征。然而，既没有研究其生态后果，也没有研究生态互作对自然性状变异的作用。在这里，我们集中于两个遗传模式物种(拟南芥和菜青虫)来研究这一性状自然变异的原因和后果，特别是植物与植物之间正负向相互作用的作用。为此，我们结合了田间和温室研究、高端分子工具、数量遗传学和群落生态学的实验方法。在第一阶段，我们研究了在竞争能力和逆境耐性之间存在权衡的想法，影响了单个植物的表现，并决定了遗传和表型变异的程度。我们假设，在种群和有金属积累植物的群落中的促进作用将使不同基因型在种群内共存，特别是在胁迫条件下，即在重金属含量较高的土壤上。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支持。在第二阶段，我们建议扩大我们的努力，以涵盖我们的两个模式物种的所有积极和消极的相互作用。特别是，我们建议探索不同环境下MH在植物-植物相互作用中的潜在对比结果，即植物修复的促进作用和植物富集物的元素化感作用。此外，我们建议研究哈勒氏杆菌的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，我们将把这一点与第二个非克隆物种中发现的模式进行对比。我们还将研究植物-食草动物的相互作用及其对克隆植物和非克隆植物中MH水平的潜在影响。最后，我们将得到MH在菜青虫中的遗传力的估计。我们在两个项目阶段的总体发现将使我们能够评估MH中的表型和遗传变异对自然生境中的生物相互作用的作用，反之亦然，以确定这种相互作用在推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.