| 英文摘要: | 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. |