Date on Senior Honors Thesis

5-2022

Document Type

Senior Honors Thesis

Degree Name

B.A.

Department

Biology

Degree Program

College of Arts and Sciences

Author's Keywords

global change; endophytes; microbiome; community ecology; fungi; nitrogen deposition

Abstract

As global change persists, changes in resource availability can influence plant-microbe interactions. To understand how resource availability can influence these interactions and species diversity, I focused this research on how varying nitrogen (N) levels affect root endophyte communities in the plant species Ammophila breviligulata, an ecosystem engineer in the dune system. I analyzed the relationship between nitrogen addition and microbial community composition across 60 plots treated with three nitrogen addition levels (control, low, and high) in a long-term experimental field site in the Lake Michigan dunes. I identified Ammophila breviligulata's root endophyte community after creating a culture collection and performing DNA analysis on samples from each of the 60 plots. Our results indicate that any level of nitrogen addition had cascading effects on the endophyte community. I identified sixteen operational taxonomic units (OTUs) and sixty-six morphospecies using genetic sequence clustering techniques. Indicator species analysis identified three species significantly associated with specific treatment levels. This research contributes novel insight to the more extensive discussion of global change and the implications of increased atmospheric nitrogen on microbial communities. Our findings will further research focused on better equipping our environment for the imminent global change threat.

Lay Summary

As global change persists, changes in resource availability have the potential to influence root fungal endophytes, which are fungal species inhabiting plant root systems. To better understand how resource availability can influence these interactions and species diversity, I focused this research on how varying nitrogen (N) levels affect root endophyte communities in the plant species Ammophila breviligulata. This plant species, known as an ecosystem engineer, is critical to the survival of the dune system. I analyzed the relationship between nitrogen addition and microbial community composition across 60 plots treated with three nitrogen addition levels (control, low, and high) in a long-term experimental field site in the Lake Michigan dunes. I identified Ammophila breviligulata's root endophyte community after creating a culture collection and performing DNA analysis on samples from each of the 60 plots. I clustered genetic sequences into sixteen taxonomic units using a statistical analysis medium before entering them into genomic databases for species identification. The data also resulted in identifying three species significantly associated with specific treatment levels. Our results indicate that any level of nitrogen addition had cascading effects on the endophyte community. This research contributes novel insight to the more significant discussion of global change and discusses the implications of increased atmospheric nitrogen on microbial communities. Our findings can further research focused on better equipping our environment for the imminent global change threat.

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