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，适应当地的环境差异可能是在不同群体的物种起源的初始阶段，如Heliconius蝴蝶，岛雀的辐射，和维多利亚湖慈鲷鱼。在这种生态物种形成模型中，自然选择作用于遗传差异，从而改善了对特定气候、土壤类型、当地竞争对手、食草动物或病原体的适应性，随后这些适应当地的种群在生殖隔离物种的轨道上分化。这个模型在解释新寄生虫物种的起源方面可能很重要，因为寄生虫不仅要适应特定的栖息地，还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尚未得到验证。本研究的目的是测试是否生态形态的基础上的物种起源的一个密切相关的组的通性寄生植物。这些物种可以附着在一系列不同的宿主植物上，并具有专门的进食器官，随后提取营养物质和水分。我们将进行实验和遗传研究英国本土Eyebrights（Euphrasia），一组21寄生物种，包括高度保护优先的类群。我们以前的研究表明，孤立岛屿上的物种表现出广泛的杂交。这项研究遵循这一发现，通过研究公平岛孤岛上的Euphrasia。这个岛屿是不同栖息地的马赛克，因此可以用来测试适应对比环境的重要性，以及这些寄生物种是否对不同的宿主植物表现出偏好。我们将首先测试三种生态专业物种在费尔岛不同栖息地生长时的表现。为了测试生存的差异是否反映了对不同宿主的适应，而不是对环境其他成分的适应，我们将在一个具有特定宿主的实验花园中种植Euphrasia。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。这将使用高通量基因组学结合更新的单分子测序技术来研究与寄生虫适应相关的遗传变化。总的来说，我们的研究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），以及这种变异背后的基因。更一般地说，寄生植物是自然系统的关键物种，因为它们的寄生性降低了竞争优势草的活力，从而维持了草地物种多样性。我们的工作将显示是否生态专门的Euphrasia适应不同的主机，这反过来可能会影响他们在草地管理中的使用。

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.