Fungi are one of the most diverse and ecologically important groups of living organisms, yet only a tiny fraction (<5%) of the estimated diversity of fungal species has been discovered and described. Fungi which live within apparently healthy plants and lichens, are thought to represent a large fraction of this unknown diversity. These symbiotic fungi are ubiquitous and ecologically important, but basic knowledge regarding their origins and evolution, rates of diversification, and metabolic capacities remains limited. The goal of this proposal is to generate DNA sequences for a diverse collection of previously unknown variety of these fungi from numerous areas to examine the evolution of major ecological modes in fungi. This study will focus on one group, the Xylariaceae, a cosmopolitan and ecologically diverse family that encompasses decomposers of wood, litter, soil and dung, plant pathogens, and numerous fungi living within plants. Furthermore, this study will investigate the metabolic capacities of these fungi and relate their carbon- and nitrogen-metabolism to their evolutionary origins and ecological modes.
This research will illuminate the evolution of large and ecologically dynamic family of fungi while also providing a first perspective on the functional biology of widespread and ecologically important symbionts of plants and lichens. Moreover, it will provide an important opportunity to mentor undergraduates in molecular and mycological techniques through the Arizona Biology Network, which provides community college students from traditionally under-represented groups with research training, and through the PI?s outreach program with Native American students in Arizona.
One of the most exciting new insights over the past 100 years is that organisms such as plants and animals harbor highly diverse communities of microbes within their healthy tissues. This is true of humans, per the human microbiome, and of plants as well. In plants, fungi are especially common inhabitants not only of roots, but also of leaves and stems. These 'endophytic fungi' are extremely diverse and frequently play important roles in plant health and stress tolerance. We are interested in the diversity, evolution, and applications of endophytic fungi. The goal of this award was to focus on one order of fungi, the Xylariales -- a group of filamentous fungi with microscopic fruiting bodies that is well known for efficient degradation of plant material -- to evaluate (1) how newly discovered endophytes change our understanding of the diversity of this group; (2) how novel our 'newly discovered' fungi really are (were they found previously?); (3) what is the typical pattern of host associations and ecological modes in this diverse group of fungi; and (4) what are the evolutionary origins of different ecological modes (plant-tissue decay, endophytism, etc.) in the lineage. We processed thousands of samples to select roughly 90 apparently novel species, and sequenced several genes for these as well as for some named taxa for which some of these data weren't available. We reconstructed the evolutionary relationships of hundreds of isolates, populating the resulting evolutionary or phylogenetic tree with endophytes for the first time. We found that most of the genera in the group are not circumscribed in a manner consistent with their evolutionary relationships. Many of the endophytes represent new lineages, and new genotypes, relative to those discovered previously. Our work detects unexpected host-generalism in the group, expands our understanding of the ecology of previously known species, and sets the stage for evaluating the abilities of these fungi to break down carbon and nitrogen in the lab -- a test of functional traits that will shed light on potential industrial applications. through this project U'Ren completed her PhD and obtained a competitive postdoctoral position. In the past year she gave four presentations, including two at national and international meetings. She published one paper based in part on this work and will submit a second paper showcasing the results of this award in August 2012. She trained a postbaccalaureate, female student whose experience supported a successful application to medical school.
