Desert Moss Breaks the Rules: New Study Finds Fungi Thriving Inside Its Cells
Researchers at the University of California, Riverside (UCR) have published evidence that a species of desert moss, Trichostomopsis australaceae, hosts fungi inside its living tissues. This finding contradicts the long-held scientific assumption that mosses do not form such internal partnerships.
"The desert is full of things people overlook. Sometimes, the biggest surprises are the ones growing quietly beneath our feet."
Discovery and Methodology
Doctoral researcher Kian Kelly collected moss samples from biological soil crusts in the Mojave and Sonoran deserts, where daytime temperatures can exceed 100°F (38°C), as well as from coastal sites near San Diego, California.
In the laboratory, researchers surface-sterilized the moss to remove external organisms. They then ground the moss tissues and searched for fungal DNA.
The analysis identified the presence of arbuscular mycorrhizal fungi (AMF), a group known to form symbiotic relationships with most land plants by exchanging soil nutrients for carbon. The fungal species detected inside the moss differed from those found in the surrounding soil, suggesting a deliberate association rather than simple environmental contamination.
Kelly then used microscopy to examine the moss cells. The study reports that the researchers observed branching fungal structures inside the moss leaves that resemble arbuscules—nutrient-exchange structures typically found in the roots of other plants.
Key Findings
- Fungal Presence: DNA from arbuscular mycorrhizal fungi was detected inside the tissue of the desert moss Trichostomopsis australaceae.
- Selective Association: The fungal species found within the moss were distinct from those present in the surrounding soil.
- Structural Evidence: Microscopy revealed arbuscule-like formations inside the moss leaf cells.
- Environmental Variation: Moss samples from coastal sites exhibited higher concentrations of AMF than samples from the driest desert locations. In the hyper-arid samples, the intracellular fungal structures were not detected.
- Unconfirmed Symbiosis: The study notes that while fungi are present inside the moss cells, it has not yet been confirmed that this is a mutualistic symbiosis. Future research is required to demonstrate whether an exchange of nutrients occurs between the organisms.
Context and Implications
Mosses are among the earliest land plants, and fungi are believed to have played a role in helping plants transition from water to land approximately 470 million years ago by providing access to nutrients.
Most land plants depend on mycorrhizal fungi to obtain phosphorus and nitrogen from the soil in exchange for carbon. This new evidence suggests that mosses, previously considered an exception to this pattern, may also participate in such partnerships.
The findings indicate that nearly all of the more than 10,000 known moss species have not been examined for internal fungi, raising the possibility of many additional hidden partnerships. If the relationship between the moss and the fungi is confirmed as a true symbiosis involving nutrient exchange, it could alter the understanding of when and how these evolutionary partnerships developed.
Possible Applications
Understanding which fungi help mosses tolerate drought and heat may provide insights for restoring damaged biological soil crusts in desert landscapes that are affected by climate change and human activity.
Statements from Researchers
Jason Stajich, a UCR professor and co-author of the study, noted that the previous scientific model held that mosses did not require fungi. Kian Kelly observed that certain fungi may be more beneficial for surviving hotter, drier climates.
"The previous scientific model held that mosses did not require fungi."
— Jason Stajich, UCR professor and co-author