Systematics and evolution of parasitic plants

寄生植物从其他被称为寄主的植物那里吸收水分和养分。一些被称为“专性”的寄生植物完全依靠寄主生存，并对它们的生长和发育产生负面影响。拟议的研究计划重点关注葫芦科植物的物种多样性和进化，这是一类在分类学上具有挑战性的专性寄生植物，包括分布在世界各地的约200种。出现分类困难的部分原因是，物种间的形态差异很小，隐藏在小花(约3毫米长)中。此外，最近记载的物种的杂交形成(网状进化)使进化历史的重建变得复杂。这一寄生群体特别重要，因为本土葫芦是其生态系统中的关键物种。然而，葫芦科植物在经济上也很重要，因为它的一些物种是农业和园艺害虫，会造成许多作物的重大产量损失。*拟议研究的第一个短期目标是揭开四个未被研究的葫芦科种群内物种水平的进化历史，并揭示在我们之前已经证明发生杂交物种形成的另外两个种群中网状进化的深度和广度。我们将使用分子和形态数据来了解物种是如何进化的，我们还将在此基础上修改它们的分类。作为这项研究的一部分，可能会发现新的物种。葫芦科的染色体数目有明显的变异(多倍体)，这项研究的第二个短期目标是阐明额外的一组染色体是如何获得的，并确定这些变化在茯丝子进化中所起的作用。由于网状进化和多倍体通常是协同工作的，染色体数据将提供更全面的了解杂交物种是如何起源的。*寄主范围是任何寄生生物的基本属性，代表了寄生虫可以攻击的寄主的总数。这项研究计划的第三个短期目标旨在首次描述卡斯库塔的寄主范围及其进化。葫芦科对寄主范围的研究一直受到阻碍，因为大多数躲避寄主侵染了许多植物科的许多寄主。为了解决这个问题，我们将从数以万计的植物标本中获得宿主数据，并使用动物寄生虫的新分析方法。总体而言，这项研究计划是正在进行的全球努力的一部分，目的是对地球上的生命进行分类，并了解其自然历史和进化。从实践的角度来看，结果将有助于更好地识别和管理来自加拿大和世界其他地区的本土和有害物种。寄主范围的结果可以用来模拟和预测蝗虫的潜在扩展。

Parasitic plants take water and nutrients from other plants called hosts. Some parasitic plants, referred to as “obligate”, depend entirely on their hosts for survival and negatively affect their growth and development. The proposed research program focuses on the species diversity and evolution of Cuscuta (dodder), a taxonomically challenging group of obligate parasitic plants comprising ~ 200 species distributed worldwide. The taxonomical difficulties of Cuscuta arise in part because the morphological variation among species is minimal and hidden inside the small flowers (~ 3 mm long). In addition, the recently documented hybrid formation of species (reticulate evolution) complicates the reconstruction of evolutionary histories. This parasitic group is particularly important because native dodders are keystone species in their ecosystems. However, Cuscuta is also economically important because some of its species are agricultural and horticultural pests that cause major yield losses in numerous crops. *** The first short-term objective of the proposed research is to unravel species-level evolutionary histories within four unstudied groups of Cuscuta, and to uncover the depth and extent of reticulate evolution in two other groups in which we have previously shown that hybrid speciation occurs. We will use molecular and morphological data to understand how species have evolved, based on which we will also revise their taxonomy. New species are likely to be discovered as a part of this research. *** Cuscuta has a pronounced variation of the chromosome number (polyploidy) and the second short-term aim of this research is to elucidate how the extra sets of chromosomes have been acquired and to identify the role that these changes had in the evolution of dodders. Since reticulate evolution and polyploidy often work in tandem, the chromosome data will provide a more thorough understanding of how hybrid species originated.*** The host range is an essential attribute of any parasitic organism and represents the totality of hosts that the parasite can attack. The third short-term objective of this research program aims to characterize for the first time the host range and its evolution in Cuscuta. The study of the host range has been hindered in Cuscuta because most dodders infest many hosts from numerous botanical families. To solve this problem, we will obtain host data from tens of thousands of herbarium specimens, and use novel analytical approaches employed in animal parasites. *** Overall, this research program is part of the ongoing global efforts to catalog life on Earth and understand its natural history and evolution. From a practical point of view, the results will facilitate a better identification and management of both native and pest Cuscuta species from Canada and the rest of the world. Host range results can be used to model and predict the potential expansion of pest dodders.