Studies on the fungal associations of the alpine sedge Kobresia myosuroides in Colorado

Kobresia myosuroides is an alpine and Arctic member of the Cyperaceae plant family and is the only known member of this family to form ectomycorrhizal (ECM) associations, yet the identity and nature of the fungi involved in these unique mutualistic relationships remains unknown.; I investigated the identity and nature of the dominant ECM symbionts of K. myosuroides during three years of sampling. Based on morphological and molecular characteristics, one symbiont was determined to be the common asexual ascomycete Cenococcum geophilum. The second common ECM type belongs to the ascomycete order Leotiales and is closely related to several recently reported isolates that may be involved in forming both ECM and ericoid-type mycorrhizae.; I used techniques based on character evolution by coding for these various types of mycorrhizae and tracing their phylogenetic distribution based on the previous phylogenetic analyses of the ITS region of the rDNA repeat. I also compared the responses of the ECM isolate from K. myosuroides to temperature and nitrogen source based on growth assays to those of other published studies of these related fungi. I conclude that there is a significant diversity both phylogenetically and in types of mycorrhizal structures associated with this group of fungi.; Over the past decade research into the dynamics of the tundra soil microbial communities of Niwot Ridge has suggested that the period surrounding spring snowmelt represents a transition between two differently adapted microbial communities. In order to better quantify and describe the differences in these soil microbial communities during the course of snowmelt I extracted total environmental DNA from soils collected at different times of the year from between tussocks of K. myosuroides. The dominant members of the soil community within this group of fungi belonged to two distinct clades of Acomycetes that have no similar known representatives in the sequence databases. These two dominant clades each seem to be associated with different temporal niches, one with pre and during snowmelt periods, and another with the plant growing season. The ECM fungal symbionts of K. myosuroides were not found to be dominant members of the bulk soil fungal community but were represented by several clones each in the pre-snowmelt and during snowmelt soils. (Abstract shortened by UMI.)...