Griffin, Eric
(2016)
THE GREATER UNSEEN: ON THE IDENTITIES, DISTRIBUTIONS, AND IMPACTS OF FOLIAR BACTERIA ON TROPICAL ARBOREAL SPECIES.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Bacteria have been called the “unseen majority” in nature. Leaves of higher plants comprise perhaps the largest bacterial substrate on earth, yet we know surprisingly little about the bacteria that occupy these spaces. The shaded understory of tropical forests is likely a “hotspot” for bacteria because water availability and humidity are high and UV radiation is low. Ultimately, these communities may be critical mediators of plant performance among co-occurring woody species and ultimately contribute to plant species distributions at the community level. In this dissertation, I (Chapter 2) review the ecology and behavior of bacteria that reside on the phyllosphere (on and inside leaves) and outline testable hypotheses to empirically evaluate the potential ecological implications of foliar bacteria. Moreover, I conducted a major effort to test interrelated hypotheses regarding the distribution, impact, and identity of foliar bacteria with replicated manipulations of N, P, and K in large experimental forest plots in Panama. To determine the net effect of foliar bacteria, I experimentally reduced bacterial in situ via the application of standard antibiotics for nearly three years. Specifically, I (Chapter 3) evaluated the degree to which soil nutrients and foliar bacteria impacted seedling growth among co-occurring woody species. Additionally, I (Chapter 4) evaluated the degree to which soil nutrients and foliar bacteria mediated leaf traits and enemy impacts among species and soil nutrient additions. Finally, I (Chapter 5) conducted a major sequencing effort to determine the degree to which host species, soil nutrients, and commercial antibiotics caused variation in bacterial endophyte community structure. Overall, my results demonstrate that there are frequent interactions between soil nutrient and foliar bacteria on plant performance and enemy impacts, which differ among host species. Further, metagenomic sequencing revealed that host species, soil nutrient additions, and antibiotics caused significant variations in bacterial community composition. For every metric, plant-bacterial interactions are largely dependent on host species and soil resource supply, a classic niche axis for species coexistence. Ultimately, my work provides evidence that foliar bacteria are an entirely independent plant functional trait that can cause critical species-specific performance outcomes, which may have important implications for plant diversity maintenance.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
29 September 2016 |
| Date Type: |
Publication |
| Defense Date: |
20 April 2016 |
| Approval Date: |
29 September 2016 |
| Submission Date: |
5 May 2016 |
| Access Restriction: |
1 year -- Restrict access to University of Pittsburgh for a period of 1 year. |
| Number of Pages: |
270 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Biological Sciences |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
diversity maintenance, tropical forest, plant-microbe interactions, community ecology, soil nutrient availability, foliar bacteria, next-generation sequencing |
| Date Deposited: |
30 Sep 2016 01:32 |
| Last Modified: |
29 Sep 2017 05:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/27914 |
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