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theses

Fungi asymptomatically infect all terrestrial vegetation, but the structure and assembly of these fungal communities are poorly understood. Smilax rotundifolia, a common woody vine of the northeastern United States, was used as a model to study endophytic (internal colonizing) and epiphytic (surface colonizing) fungal communities, from the perspectives of niche-based influences, spatial variation, and evolutionary relationships. Wild greenbrier plants were sampled in New Jersey (USA) in late winter at a single site, and again in mid-summer, in a multi-site, multi-tissue, sampling effort. Fungal communities of the plant surface and interior were made up of mostly different species. Correlative relationships were found between some fungal species' abundances, but none were seen between species that were strongly restricted to the surface and those strongly restricted to the interior. The summer, multi-site study, revealed that the strongest factor determining fungal community composition was surface vs. interior habitat, followed by tissue/organ type, and lastly general geographic location. The effect of season was also studied by comparing the single-site winter dataset against the data from the same site sampled in summer. Season had a major influence on some fungal species but not others, similar to influence of tissue type. Also, in a very novel finding, it was found that certain endophytes showed statistically different abundances, depending on the distance from the stem base at which a sample was taken. The optimum height differed for different fungal species. At the scale of a single stand of plants, it was found that epiphytic, but not endophytic, samples showed a significant correlation between spatial proximity and fungal community similarity. Finally, the phylogenetic relationships were studied between congeneric fungal species that were common on the plant. Two-gene phylogenies were constructed using Smilax-derived isolates, along with downloaded sequences of well-defined species in the same genera. These congeneric species were found to be only distantly related (i.e., they were widely separated within the known phylogenies of their genus). The final chapter is a literature review, bringing insight from the present dissertation research to identify important unanswered questions. Evidence for the role of plant secondary metabolites on endophytic fungi is discussed.

ETD_6799

Ph.D.

Includes bibliographical references

by Christopher B. Zambell

doi:10.7282/T38P62H9

ETD doctoral

The author owns the copyright to this work.