Systematics and evolution of parasitic plants

寄生植物从被称为寄主的其他植物那里吸取水分和营养。一些寄生植物，被称为“专性”，完全依赖其宿主生存，并对其生长和发育产生负面影响。拟议的研究计划侧重于菟丝子（菟丝子）的物种多样性和进化，这是一组具有分类学挑战性的专性寄生植物，包括分布在世界各地的约200种。菟丝子分类学上的困难部分是因为物种之间的形态变化很小，隐藏在小花（~ 3 mm长）中。此外，最近记录的物种杂交形成（网状进化）使进化历史的重建变得复杂。这一寄生类群特别重要，因为本地菟丝子是其生态系统中的关键物种。然而，菟丝子在经济上也很重要，因为它的一些物种是农业和园艺害虫，导致许多作物的主要产量损失。*** 拟议的研究的第一个短期目标是解开物种水平的进化历史内四个未研究的组的菟丝子，并揭示在其他两个组中，我们以前已经表明，杂交物种形成的网状进化的深度和程度。我们将使用分子和形态学数据来了解物种是如何进化的，在此基础上，我们还将修改它们的分类法。作为这项研究的一部分，可能会发现新的物种。*** 菟丝子有一个显着的变化的染色体数目（多倍性）和本研究的第二个短期目标是阐明如何获得额外的染色体组，并确定这些变化在菟丝子的进化中的作用。由于网状进化和多倍性通常是协同工作的，染色体数据将为杂交物种的起源提供更透彻的理解。 宿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宿主的总数。本研究计划的第三个短期目标旨在首次描述菟丝子的宿主范围及其演变。菟丝子寄主范围的研究一直受到阻碍，因为大多数菟丝子侵染来自众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标本馆标本中获得宿主数据，并使用新的分析方法在动物寄生虫。*** 总的来说，这项研究计划是正在进行的全球努力的一部分，以编目地球上的生命，并了解其自然历史和进化。从实用的角度来看，这些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地和害虫菟丝子物种。寄主范围的结果可以用来模拟和预测害虫菟丝子的潜在扩张。

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.