DISSERTATION RESEARCH: Investigating life history and environmental drivers structuring host-associated assemblages of mycorrhizal and endophytic fungi in subalpine tree islands

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Prior to recent advances in DNA sequencing technologies, scientists could never have imagined the vast microbial diversity associated with each individual plant and animal. Rather than individual discrete organisms, all higher organisms are home to diverse consortia of microscopic bacteria and fungi, called microbes. From our mouths to plants' leaves, unique communities of microorganisms play important roles in higher organisms'ability to function. This research focuses on understanding the mechanisms driving the community structure of the fungi associated with the leaves of plants (foliar endophytes) and beneficial fungi associated with the roots of trees (ectomycorrhizal fungi). This research has broad ranging societal impacts by uncovering fungal diversity that can be helpful to improving tree health, ecosystem stability, and resilience to climate change. One of the focal trees in this study, the white bark pine, is a foundation species central to ecosystem function in subalpine environments. White bark pine trees are highly threatened by a combination of blister rust, mountain pine beetles, and climate change. Foliar endophytes are known to improve the resistance of trees to both disease and temperature fluctuations caused by climate change. Thus, uncovering the diversity of foliar endophytes associated with these trees has the potential to lead to beneficial treatments for this endangered tree species. In addition, this project also has strong educational and outreach components. Students involved in the proposed work will gain experience with fieldwork and cutting edge DNA sequencing methods. Despite being incredibly important drivers of plant community composition and ecosystem function, little is known about the basic biology or patterns of diversity of these fungi. This project applies cutting edge next generation sequencing technologies to isolated pine trees located in Yosemite National Park to answer important questions about the community structure, diversity, and basic biology of these fungi. Here a simple host-island setting is used to test for the effect of dispersal distance, host type, environment (host physiology, soil chemistry & season), on community structure in two host-dependent guilds of fungi. The main aim of this proposal is to compare the relative effects of niche versus dispersal assembly in two functional guilds of host-associated fungi.