Identifier

etd-01252012-112627

Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

This dissertation explores the effects of stress and disturbance on fungal endophyte diversity and composition in obligate wetland plants in southeast Louisiana. I explored two types of endophytes: root and foliar. Each of these groups is known to live within apparently healthy host plants without causing symptoms of disease; therefore, plants are thought to benefit from this association. Few studies, however, have shown that plants in wetlands associate with fungi. In this dissertation, I show that both root and foliar endophytes not only exist in wetland plants living in flooded and saline environments, but also are abundant within these plants. In the chapter two I explore the distribution of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in the roots of 18 plant species. Monocots were mostly colonized by DSE, and dicots, including woody species were mostly colonized by AMF. In the third chapter, I used a mesocosm approach, to explore the effects of soil conditions on foliar endophyte diversity and composition in two wetland plant species – Sagittaria lancifolia and Taxodium distichum. Endophytes were abundant in both hosts, but S. lancifolia contained higher diversity. In addition, endophyte composition was shaped by different factors in each host: water quality shaped communities in T. distichum, and hydrology in S. lancifolia. In the fourth chapter I expand on the third chapter by including four more plant species that range from highly salt tolerant to intolerant and simulated a category 3 hurricane to explore its effects on endophytes within each plant species. I found that endophytes of grasses, irrespective of salt tolerance, did not change in diversity or composition following the simulated hurricane. Endophyte diversity T. distichum did not change, but composition was dependent on habitat type. Sagittaria lancifolia’s endophyte diversity decreased with hurricane conditions, but overall composition did not change. The results of these studies not only demonstrate that endophytes are present in wetland plants, but that they are abundant and common. Further, I show that host identity interacts with environmental conditions to influence diversity and composition and that habitat type is important in determining the outcome of endophyte composition after hurricanes.

Date

2012

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Platt, William J.

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