The role of allelopathy in plant invasion: evolutionary change vs. community response in Impatiens glandulifera

入侵植物在其入侵范围内竞争性地排斥邻近植物，对生物多样性和生态系统过程构成重大威胁。化感作用是植物释放的化学物质对邻近植物的抑制作用，被认为是促进植物入侵成功和竞争优势的机制。特别是，新武器假说（NWH）认为，由于缺乏共同适应，一些入侵植物产生的化感物质对其入侵范围内的邻居来说是新颖的，因此提供了竞争优势。然而，在入侵植物的研究中，一个被高度忽视的方面是化感能力增强的可能进化。在入侵范围内，由于它提供的竞争优势以及从病原体和食草动物等专门敌人中释放出来的结果，预计化感化学物质的快速进化会增加。在这里，我建议进行一项全面的研究，以检验欧洲最具侵略性的植物之一——凤仙花（Impatiens glandulifera）——的NWH和进化增强化感作用的假设，凤仙花的化感作用虽然得到了承认，但尚未完全确定。化感作用在该物种成功入侵中的作用将在一系列新的实验中确定，这些实验将比较本地和入侵基因型的化感物质产生的变化，以及本地和入侵范围内的群落对这些化学物质的反应。本研究将解决一些对入侵植物研究至关重要但仍很少研究的关键问题。这包括在整个生物地理范围内对共存植物和土壤生物群的化感作用，以及在入侵初期和后期之间的整个入侵过程。该研究还将探讨入侵和本地基因型中化感和抗草食化合物产生之间的潜在遗传相关性。本研究的结果将有助于深入了解腺芽瓢虫的入侵特性，因为目前几乎没有关于其入侵特征和群落反应的生物地理差异的知识。研究结果有助于加深我们对其入侵过程的认识，阐明影响入侵过程的进化力量，并为控制腺蠓的管理实践提供建议。

Invasive plants present major threats to biodiversity and ecosystem processes as they competitively exclude neighbouring plants at their invasive range. Allelopathy, which is the suppression of neighbouring plants by plant-released chemicals, has been suggested as a mechanism facilitating their invasive success and competitive superiority. Particularly, the Novel Weapons Hypothesis (NWH) suggests that the allelochemicals produced by some invasive plants are novel to their invasive-range neighbours due to lack of co-adaptations, and hence provide a competitive advantage. However, a highly neglected aspect in the study of invasive plants is the possible evolution of increased allelopathic ability. Such rapid evolution of increased allelochemical production at the invasive range is predicted due to the competitive advantage it provides and as a result of release from specialist enemies, such as pathogens and herbivores. Here, I suggest a comprehensive study that will examine both the NWH and the hypothesis of evolutionary increased allelopathy in one of the most invasive plant species in Europe, Impatiens glandulifera, whose allelopathic effects, though recognized, are not yet fully established. The role of allelopathy in the invasive success of this species will be determined in a set of novel experiments that will compare both changes in the production of allelochemicals by native and invasive genotypes as well as the responses of the native and invasive-range communities to these chemicals. This study will address some key aspects that, although crucial to the study of invasive plants, are still seldom studied. These include the allelopathic effects on both coexisting plants and soil biota across the biogeographic range as well as across the invasion process between initial and late stages of invasion. The study will also address the potential genetic correlation between the production of allelopathic and anti-herbivore-compounds in invasive and native genotypes. The results of this study are expected to yield insight as to the invasive nature of I. glandulifera, for which almost no knowledge is available on biogeographic differences in either its invasive characteristics or the community response to it. The overall findings could enhance our understanding of invasion process and elucidate the evolutionary forces determining them as well as provide recommendations for management practices for control of I. glandulifera.