PELLSTON, Mich. — To the naked eye, a leaf on a tree may look like a paper-thin sheet of green. However, a microscope reveals a robust world made up of miniscule hair or feather-like structures that shelter tiny mites who play a mighty role in defending the tree.
University of Michigan researchers and undergraduate students have been exploring that alliance in the forests surrounding the U-M Biological Station, a historic research and teaching campus in northern Michigan.
Their study, published in the peer-reviewed journal Symbiosis, suggests that some trees invest less in chemical defenses when they provide housing for protective mite “bodyguards.”
“Mites may seem like a common pest, but there are many species that are pretty helpful for trees to have around,” said Dr. Marjorie Weber, an associate professor in the U-M Department of Ecology and Evolutionary Biology and the instructor of the “Insights from Trees” class at UMBS.
The research was integrated into the four-week field course, which brings together undergraduates from across the humanities, arts and sciences. No prerequisites are required. Students examine trees through ecological, artistic and societal perspectives while completing a hands-on research project.
“Before I saw nature as something to just pass by, but now I could really go in depth and understand that there is so much life surrounding me, and all of it is interconnected in different ways,” said Abigail Adams, who was a second-year psychology student at Schoolcraft College when she took the Insights From Trees class at UMBS in July 2025. “It absolutely changed my perspective on life.”
Weber has taught Insights from Trees each summer since 2024. Every student enrolled in the 2024 and 2025 courses became a co-author of a peer-reviewed scientific paper.
The 2024 class evaluated the abundance of mites on the foliage of woody plants, with its findings published in the journal Ecology and Evolution. The 2025 class examined the relationship between mite housing and trees’ chemical defenses, resulting in the new Symbiosis paper. The summer 2026 class extended that work, and its results are being analyzed with the goal of submitting a third publication with student authors.
For each project, students help develop research methods, shape the study design and collect data. All fieldwork takes place within one kilometer of UMBS’s main campus along Douglas Lake, where the surrounding oak-maple-beech forest serves as both classroom and laboratory.
Tiny Homes on Leaves
The researchers studied structures called mite domatia. Found on the undersides of some leaves, domatia are small pockets or tufts of hair located in the crooks where leaf veins meet. These microscopic shelters house mites that can benefit trees by eating pests and fungi.
It is a tiny version of a familiar ecological exchange: The tree provides housing, and the mites provide protection.
Mite domatia occur in an estimated 10% of woody plant species worldwide and appear in fossils dating to the Cretaceous Period, Weber said. Yet they remain understudied compared with other plant-animal partnerships, such as those between flowers and pollinators.
For the study published in Symbiosis, the summer 2025 class examined eight common deciduous tree species growing on UMBS property, including sugar maple, basswood and chokecherry.
They combined field observations with two advanced laboratory methods. Using scanning electron microscopy, they produced highly magnified images of the microscopic leaf hair or feathers, known as trichomes. They also used chemical metabolomics to create detailed fingerprints of defensive compounds within the leaf tissue.
Together, those approaches allowed the team to investigate whether trees face an evolutionary tradeoff between two forms of protection: making chemical defenses themselves or recruiting beneficial mites to help.
Chemical Armor or Animal Allies
The results supported that hypothesis. Tree species with mite domatia had about 34% lower levels of total phenolics and 18% lower overall abundance of defense-related compounds than species without domatia.
Phenolics are a broad group of chemicals that can help protect plants against insects, pathogens and other threats. But defensive chemicals may also deter or harm beneficial organisms. A tree that depends on resident mites may need to avoid filling their home — and food supply — with compounds that could poison its bodyguards.
The researchers also found evidence that the hairs forming mite domatia are specialized structures, not ordinary leaf hairs that happen to grow in a convenient place.
On individual leaves, the hairs making up the mite shelters were 24% to 31% longer than hairs elsewhere on the same leaf. The pattern appeared across distantly related tree species, suggesting that the specialized hairs evolved independently multiple times.
That process is called convergent evolution: Different species arrive at similar solutions when they face similar ecological challenges. Wings in birds and bats are a familiar example.
In this case, several tree lineages appear to have independently evolved longer hairs where their leaf veins meet, creating homes for protective mites.
The pattern was reversed in tree species without domatia. In those control species, hairs at the junctions of leaf veins were shorter than hairs elsewhere on the leaf.
Published in June 2026, the study is the first comparative investigation to examine both fine-scale leaf chemistry and trichome traits across multiple independent evolutionary origins of mite domatia. The findings offer new insight into how partnerships between plants and animals can shape physical and chemical traits over evolutionary time.
The research may also have practical implications. A better understanding of how plants balance chemical defenses with protection from beneficial organisms could eventually support more sustainable approaches to managing pests and disease in agriculture and forestry.
Students Doing Science
“Students at the University of Michigan Biological Station do more than just learn about the scientific process, they participate in every step of the research and answer real scientific questions,” said Dr. Aimée Classen, director of UMBS and a professor of ecology and evolutionary biology at U-M. “I’m proud of the work done by the Insights from Trees class to advance the broader understanding of plant defense and evolution.”
Dominick Noeker, who was a U-M sophomore when he took the course in July 2025, said the experience helped shape his career goals.
“It is an opportunity unlike anything else,” Noeker said. “The Biological Station is the reason I went to Michigan, and it has had a huge influence on my career aspirations. It connected me with researchers and professors who I’ve kept in touch with. Research of any kind is competitive, and the Biological Station allowed me to dip my toes into that world and build my résumé for future work.”
The research was funded by a National Science Foundation (NSF) CAREER grant awarded to Weber. U-M Ecology and Evolutionary Biology graduate students Rosemary Glos and Abrianna Soule, the study’s co-first authors, also received support through the NSF Graduate Research Fellowship Program (GRFP).
The undergraduate co-authors from the 2025 UMBS class are: Abigail Adams, Macy Arnett, Josephine Eckman, Quinn Hane, Avery Logan, Emma Morterud, Dominick Noeker, William Ugorji, Elizabeth Vanostran, Avalon Yuhas, and Rae Zosel. Co-author and UMBS alum Christopher Talbot was a technician in Weber’s lab in July 2025.
The University of Michigan Biological Station serves as a gathering place to learn from the natural world, advance research and education, and inspire action. We leverage over a century of research and transformative experiences to drive discoveries and solutions to benefit Michigan and beyond.
Our vast campus engages all of the senses. Its remote, natural setting nurtures deep thought and scientific discovery.
Founded in 1909, UMBS supports long-term research and education through immersive, field-based courses and features state-of-the-art equipment and facilities for data collection and analysis to help any field researcher be productive. It is where students and scientists from across the globe live and work as a community to learn from the place.
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