Ectomycorrhizal (EM) fungi of Quercus douglasii: Diversity, spatiotemporal dynamics, and new and interesting taxa

This Ph.D. dissertation documents the diversity and spatiotemporal dynamics of the ectomycorrhizal (EM) fungal community in a Mediterranean woodland dominated by Quercus douglasii (blue oak). Although Quercus woodlands are key components of California's wild landscapes, little is known about their associated fungi. The first two chapters of this dissertation focus on the taxonomy and ecology of new and interesting taxa that inhabit Quercus woodlands. Chapter one describes Gymnomyces xerophilus sp. nov., a rare false-truffle that fruits and forms EM with Quercus species. Chapter two focuses on Genea and Genabea, two related genera of hypogeous Pyronemataceae that are abundant and diverse as sporocarps and on EM roots of Quercus. Chapter two also provides evidence that Genea intermedia, a species poorly accommodated within either Genea or Genabea, merits separate recognition in the newly erected genus Gilkeya. The third chapter details the diversity and temporal dynamics of the EM community of Q. douglasii as assessed by rDNA sequence analysis of pooled roots and sporocarps. Results suggest that the EM community associated with Q. douglasii is heavily influenced by the Mediterranean climate, with most of the dominant EM fungi producing small, inconspicuous sporocarps. This study detected a large number of Ascomycota and hypogeous taxa relative to previous EM community studies. However, despite the erratic weather at the study site, the EM community on the roots of Q. douglasii remained relatively stable over two years. Data presented here suggests that seasonally dry woodlands host a diversity of EM fungi similar to or greater than more mesic forests. The level of diversity in these xeric EM systems has probably been underestimated in the past because many of the EM fungi produce cryptic sporocarps that are difficult to locate and differentiate from one another based on morphology.