A newly published peer-reviewed study co-authored by Warren Wilson College faculty and recent graduates explores a little-known but essential part of forest ecosystems: fungal endophytes, the microscopic fungi that live inside leaves and help plants use water more efficiently.
The study, titled “Site-Based Patterns of Variation in Leaf Endophytes and Ecophysiological Performance in Sweet Birch (Betula lenta L.) in the Southern Appalachian Mountains, USA: A Preliminary Study,” investigates how these fungi—and the trees they live in—experience water stress across elevation gradients in the southern Appalachians. As climate change alters precipitation patterns and increases the frequency of droughts, understanding how trees and their fungal partners respond to these stresses becomes essential for managing forest health. By revealing how sweet birch trees face increasing water stress at higher elevations and how their microbial communities vary across these gradients, the study highlights the interconnectedness of climate factors and plant survival in an era of environmental change.
What Are Endophytes—and Why Do They Matter?
Endophytes are tiny fungal microbes found in the leaves of almost every land plant. Though invisible to the naked eye, they play an important role in helping plants survive, especially by improving their ability to absorb and use water. This function is becoming increasingly critical as climate change continues to alter water availability in forests across the world.
Warren Wilson researchers focused on Betula lenta, or sweet birch, a native tree recognizable by its smooth bark and root beer-like aroma when scratched. Their goals: to find out if sweet birch trees experience greater water stress at higher elevations, and whether the makeup of their leaf-dwelling fungal communities shifts with those changes in elevation.
Fieldwork, Fungi, and DNA
The team measured photosynthesis and gas exchange in leaves from trees growing at various elevations in Pisgah National Forest, using a portable device that clamps onto leaves to measure their physiological performance. Back in the lab, they cultured fungi from the leaves and used DNA barcoding—a method that identifies species by specific genetic markers—to analyze and compare endophyte communities across different sites.
Their results confirmed that sweet birch trees do, in fact, experience more water stress as elevation increases. They also found differences in the fungal communities inhabiting those trees’ leaves—suggesting that these microbial partners may respond to environmental pressures in tandem with their host plants.
“Appalachian forests are widely considered to be biodiversity hotspots – and home to so many plant and animal species. Fungal endophytes are incredibly common in nature, so it was a huge surprise to learn how little is known about this ecological relationship in our region,” explained Dr. Hove.
Student-Driven Science and Lasting Mentorship
Two Warren Wilson students were central to this research: Grace Dougherty ’23, now a research scientist at the Smithsonian Ecological Research Center, and Grace Zaboski ’24, who works in science communication in both Vermont and California. Both began the project during their time at Warren Wilson as part of the College’s Natural Science Undergraduate Research Program (NSURS).
Zaboski’s involvement began unexpectedly, after her original NSURS project was lost to contamination. “It was a huge upset,” she said. “I had already spent 40+ hours on that project and was very attached to the material I was studying.” But her faculty mentor, biology professor Alisa Hove, saw Zaboski’s passion and commitment and offered her the opportunity to pick up Dockerty’s earlier research on endophytes.
“I was so grateful and excited to work on the genetic components of Grace’s research,” Zaboski said. “I absolutely loved learning about PCR [Polymerase Chain Reaction] and how it can be used for identification.” For her senior presentation, she shared results from 26 unique fungal samples she identified using Sanger sequencing.
After graduation, Zaboski continued working closely with Hove and Dougherty to turn their individual research into one cohesive study. “There was always something so special about pausing whatever I was doing in the chaos of post-graduation life to commit my attention to two women I deeply admire for the excellence they pour into their work,” she said. “Their trust in me has strengthened my confidence in my ability as a scientist.”
Dr. Hove underscored the importance of student collaboration: “This project wouldn’t have happened without Grace Dougherty’s fascination with leaf endophytes. My previous research in this area focused on mycorrhizal fungi in roots. It’s a great example of how my students inspire me to continue exploring new directions in research. Having Grace and Zaboski as alumni partners made the work even more meaningful—we were a great team during the research and an even better one writing the article afterward.”
Faculty member Eric Griffin later joined the team as a coauthor, adding ecological expertise to help sharpen the paper’s analysis and conclusions.
A Microscopic Clue to Forest Resilience
This is one the first study to investigate fungal endophytes in sweet birch in the southern Appalachians, a region where these kinds of plant-microbe relationships remain largely unstudied. Though the research is preliminary, it points to a potentially important factor in how forests respond to climate change—and how we might better manage and conserve them moving forward.
“It’s one of the coolest parts of going to Warren Wilson,” Zaboski said. “Your teachers make the effort to know you and foster your strengths. It isn’t just luck that I was put on this project—it was an active recognition that I was up to the task.”