Ecological speciation and host adaptation in a parasitic plant

生物学研究的一个主要目的是了解新物种是如何进化的。最近的研究表明，对当地环境差异的适应可能是不同种群物种起源的初始阶段，如蝴蝶、岛雀的辐射和维多利亚湖慈嘴鱼。在这种生态物种形成模型中，自然选择作用于遗传差异，这些差异赋予特定气候、土壤类型、当地竞争对手、草食动物或病原体更好的适合性，随后这些适应当地的种群在走向繁殖隔离物种的轨迹上出现分歧。这个模型可能对解释新寄生虫物种的起源很重要，因为寄生虫不仅要适应特定的栖息地，而且要适应栖息地内的宿主范围。然而，生态物种形成在寄生虫中的作用在很大程度上仍未得到检验。这项研究的目的是检验生态物种形成是否是一组密切相关的多面性寄生植物物种起源的基础。这些物种可以通过一个专门的摄食器官附着在一系列不同的寄主植物上，然后提取养分和水分。我们将对英国本土眼镜蛇进行实验和遗传学研究，这是一组由21个寄生物种组成的群体，包括高度保护优先的分类群。我们之前的研究表明，与世隔绝的岛屿上的物种表现出广泛的杂交。这项研究是在这一发现的基础上进行的，研究对象是费尔岛孤岛上的幼发拉西亚。这个岛是不同生境的马赛克，因此可以用来测试适应不同环境的重要性，以及这些寄生物种是否表现出对不同宿主植物的偏好。我们将首先测试三个生态专业物种在公平岛不同生境中的表现。为了测试存活的差异是否反映了对不同宿主的适应，而不是对环境的其他成分的适应，我们将在一个有特定宿主的试验性花园中种植大戟。最后，我们将通过对自然种群进行基因组测序来研究适应和物种形成的遗传学。这将结合高通量基因组学和较新的单分子测序技术来研究与寄生虫适应相关的基因变化。总体而言，我们的结果将为寄生植物物种的起源提供重要的新见解。我们的研究从多个角度解决了这个问题，揭示了自然选择压力的类型(如切换宿主偏好)，以及导致这种变异的基因。更广泛地说，寄生植物是自然系统的关键物种，因为它们的寄生性质降低了竞争优势草的活力，从而维持了草原物种的多样性。我们的工作将显示生态专门化的幼发拉西亚是否适应不同的宿主，这反过来可能会影响它们在草原管理中的使用。

A major aim of biological research is to understand how new species evolve. Recent research suggests that adaptation to local environmental differences could be the initial stage in the origin of species in diverse groups such as Heliconius butterflies, radiations of island finches, and Lake Victoria cichlid fish. In this model of ecological speciation, natural selection acts on genetic differences that confer improved fitness for a given climate, soil type, local competitor, herbivore or pathogen, and subsequently these locally adapted populations diverge on a trajectory towards being reproductively isolated species. This model could be important in explaining the origin of new parasite species, as parasites will not only have to adapt to the specific habitat, but the range of hosts within a habitat. However the role of ecological speciation in parasites remains largely untested. The objective of this research is to test whether ecological speciation underlies the origin of species in a closely related group of generalist parasitic plants. These species can attach to a range of different host plants with a specialised feeding organ and subsequently extract nutrients and water. We will perform experimental and genetic studies on British native eyebrights (Euphrasia), a groups of 21 parasitic species including taxa of high conservation priority. Our previous research has shown species on isolated islands show extensive hybridisation. This research follows on from this finding, by studying Euphrasia on the isolated island of Fair Isle. This island is a mosaic of different habitats, and as such can be used to test the importance of adaptation to contrasting environments, and whether these parasitic species show preferences for different host plants.We will first test the performance of three ecologically specialised species when grown in different habitats on Fair Isle. To test whether differences in survival reflect adaptation to different hosts, rather than adaptation to other components of the environment, we will grow Euphrasia in an experimental garden site with specific hosts. Finally, we will investigate the genetics of adaptation and speciation by performing genome sequencing of natural populations. This will use high-throughput genomics in conjunction with newer single-molecule sequencing technologies to investigate the genetic changes associated with parasite adaptation.Overall, our results will give important new insights into the origins of parasitic plant species. Our research tackles this issue from multiple angles, revealing the type of natural selection pressure (such as switching host preferences), as well as the genes underlying this variation. More generally, parasitic plants are keystone species of natural systems, as their parasitic nature reduces the vigour of competitively dominant grasses, and thus maintains grassland species diversity. Our work will show whether ecologically specialised Euphrasia are adapted to different hosts, which may in turn affect their use in grassland management.