acase@tulane.edu / Microbial organisms are powerful symbionts of macroorganisms due to their high abundance and diversity in every ecosystem as well as their wide range of metabolic pathways. Microbes have the potential to affect host fitness, and the microbial community function can range from mutualist to pathogenic. The composition of the community may be determined by the local microbial diversity, host-level selection, and effects of environmental chemistry and ambient conditions. In this dissertation, I use two systems, leaf-cutting ants and Jatropha curcas, to determine the factors driving symbiotic microbial community assembly as well as assess the effects of the microbial community on host characteristics. With leaf-cutting ants, I collected microfungi acting as symbionts within the leaf-cutting ant system through leaf-tissue symbionts (endophytes) and fungal garden/ant colony contaminants. Through micro-colony assays, my data suggest that the worker ants moderate their behavior in a species-specific rather than generalized fashion when responding to different types of microfungi. This demonstrates the power of a biotic selective agent in driving the microbial community assembly. With J. curcas, I use field and greenhouse studies to compare assembly of bacterial symbionts as well as greenhouse studies to assess the effects of different soil microbial guilds. I found the bacterial community within J. curcas is plastic and is influenced by major plant nutrients, the soil microbes, and the ambient environment. In the field, where the ambient environment was not constant and where environmental stresses were the strongest, we saw divergence in community based on location. In a greenhouse experiment, we grew J. curcas in soil with high microbial (fungal and bacterial) diversity, low microbial diversity, AMF diversity, and bacterial diversity (fungi suppressed). We found that soil with the highest diversity of microbes hampers plant growth, but AMF alone can increase plant growth. However, we saw no evidence for the ability of soil microbiota to increase resistance to generalist foliar pathogens. These studies highlight the importance of examining multiple factors influencing microbial community assembly and microbial effects on host traits. / 1 / Kimberly Mighell
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_76384 |
| Date | 2017 May 1900 |
| Contributors | Mighell, Kimberly (author), Van Bael, Sunshine A. (Thesis advisor), School of Science & Engineering Ecology and Evolutionary Biology (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic, 93 |
| Rights | No embargo, Copyright is in accordance with U.S. Copyright law. |
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