Dynamical interactions between plant and oomycete biodiversity in a temperate forest

了解如何保持森林中树木的多样性是一项全球性挑战。虽然入侵害虫和病原体引起的新疾病的影响可能是巨大的，但对本地害虫和疾病的更微妙的影响却知之甚少。例如，本地病原体和害虫是否可以通过限制最常见的树种，在森林中为稀有物种创造空间，从而促进（而不是破坏）生物多样性？该项目将侧重于本地病原体的作用，称为卵菌，在保持树木的多样性，在太平洋西北部的老增长的森林。卵菌，或水霉菌，是高度破坏性的真菌样植物病原体，最有名的是造成爱尔兰马铃薯饥荒在19世纪50年代。虽然众所周知的农业病原体，卵菌是原生的，并在许多森林丰富。然而，人们对它们在天然森林中的生态作用几乎一无所知。该项目将（i）记录存在于华盛顿州南部风河古老森林中的卵菌物种，（ii）确定每种卵菌物种攻击或限制森林中不同类型树种的能力，以及（iii）利用现代遗传技术探索卵菌如何适应不同类型的树种。通过整合所有这些信息，研究人员将更好地了解卵菌和其他病原体在森林中的作用。这一认识将改善对自然生态系统的管理和其中发生的疾病。该项目还将培训本科生、研究生和博士后学生，使用培养和非培养方法对植物和卵菌进行初步普查，并对植物和卵菌进行基因分型，将导致植物接种实验，以确定卵菌的宿主范围。基因组和转录组测序将研究窄宿主范围卵菌可能适应优势宿主植物物种遗传多样性的机制，并将更深入地研究宽宿主范围卵菌如何适应其栖息地的植物物种多样性。 一个特别的重点将是地方性的广泛的主机范围卵菌的作用，以及它们的相互作用与优势和非优势宿主物种可能有所不同。通过整合分类，遗传，基因组和功能的卵菌和植物在风河网站的信息，卵菌在影响植物生物多样性的可能作用的两个广泛的假设将进行测试。这两个假设是：（A）寄主范围狭窄和广泛的病原体可能会降低优势寄主的适合度，从而促进植物物种和遗传多样性。 (B)优势宿主可能受益于广泛的宿主范围病原体的存在，由于对广泛的宿主范围病原体的上级抗性或耐受性。（A）和（B）两者可以独立地对病原体的不同物种或甚至菌株起作用。

Understanding how the diversity of trees in forests is maintained is a global challenge. While the impact of invasive pests and new diseases caused by pathogens can be dramatic, the more subtle impacts of native pests and diseases are poorly understood. For example, can native pathogens and pests help promote (rather than destroy) biodiversity by limiting the most common tree species, creating room in the forest for rare species that would otherwise be outcompeted? This project will focus on the role of native pathogens, called oomycetes, in maintaining tree diversity in an old growth forest in the Pacific Northwest. Oomycetes, or water molds, are highly destructive fungus-like plant pathogens, best known for causing the Irish potato famine in the 1850s. Though well known as agricultural pathogens, oomycetes are native to and abundant in many forests. However, almost nothing is known about their ecological roles in natural forests. This project will (i) document the oomycete species present in the Wind River old growth forest in southern Washington state, (ii) determine the ability of each oomycete species to attack or limit different types of tree species in the forest, and (iii) use modern genetic techniques to explore how oomycetes may adapt to different types of tree species. By integrating all this information, the researchers will develop a better understanding of the roles of oomycetes and other pathogens in forests. This understanding will improve management of natural ecosystems and the diseases that occur within them. The project will also train undergraduate, graduate and postdoctoral students.An initial census of plants and oomycetes, using both culturing and culture-independent methods, together with genotyping of the plants and oomycetes, will lead to plant-inoculation experiments that will identify the host ranges of the oomycetes. Genome and transcriptome sequencing will examine the mechanisms by which narrow host range oomycetes may adapt to genetic diversity in the dominant host plant species, and will examine more deeply how broad host range oomycetes may adapt to a diversity of plant species in their habitat. A particular focus will be on the role of endemic broad-host-range oomycetes, and how their interactions with dominant and non-dominant host species may differ. By integrating taxonomic, genetic, genomic and functional information about the oomycetes and plants at the Wind River site, two broad hypotheses regarding possible roles of oomycetes in influencing plant biodiversity will be tested. The two hypotheses are: (A) Narrow and broad host range pathogens may reduce the fitness of dominant hosts and so promote plant species and genetic diversity. (B) Dominant hosts may benefit from the presence of broad host range pathogens due to superior resistance or tolerance to broad-host-range pathogens. Both (A) and (B) may operate independently for different species, or even strains, of pathogens.