The biggest surprises are the ones growing quietly beneath our feet
For over a century, mosses were regarded as the solitary survivors of the plant world — ancient, rootless, and unbeholden to the fungal partnerships that sustain most of life on land. Now, researchers at UC Riverside have found evidence of mycorrhizal fungi living inside desert moss tissues, quietly overturning that assumption. The discovery, drawn from the living crusts of the Mojave and Sonoran deserts, suggests that even the most seemingly self-sufficient organisms may be woven into relationships we have not yet learned to see — and that the story of how life first claimed dry land may need to be told again.
- A foundational assumption of botany — that mosses survive without fungal partners — has been contradicted by DNA analysis and microscopy revealing fungi living inside desert moss cells.
- The fungi found are not surface contaminants but mycorrhizal species, forming structures inside moss leaves that resemble the arbuscules normally built inside plant roots — structures that have no business being there, by the old rules.
- Desert mosses harbor distinctly different fungal communities than their non-arid counterparts, raising urgent questions about whether these partnerships help plants endure extreme heat and dryness as global drylands expand.
- Researchers are now working to prove that mosses and fungi actually exchange resources, a confirmation that would transform the finding from striking correlation into demonstrated symbiosis.
- If the relationship holds, it could rewrite the evolutionary history of land colonization 470 million years ago and open new strategies for restoring the fragile biological soil crusts that stabilize desert ecosystems worldwide.
Beneath the surface of the Mojave and Sonoran deserts, where temperatures exceed 100 degrees Fahrenheit and the ground forms a thin living crust of mosses, bacteria, and algae, UC Riverside doctoral researcher Kian Kelly made a discovery that quietly dismantles a century of botanical consensus. Mosses — long celebrated for their almost supernatural resilience, their ability to desiccate and revive, to cling to bare rock without roots or apparent help — were believed to be the one major plant group that lived without fungal partners. Kelly decided to test that belief.
Collecting specimens from biological soil crusts, those fragile living skins of drylands so delicate that a single footprint can scar them for decades, Kelly ground up moss tissue and searched for fungal DNA. What he found was not only fungi inside the moss, but mycorrhizal fungi — organisms known to depend on plant partnerships for survival. The communities inside desert mosses were distinct from those in surrounding soil and from fungi found in mosses of milder climates, suggesting something more purposeful than contamination.
To see beyond the DNA, Kelly stained moss tissue and examined it under a microscope. Inside the cells — not the roots, because mosses have none, but the leaves — he found branching fungal structures resembling arbuscules, the tree-like formations mycorrhizal fungi typically build inside plant roots. The researchers describe them carefully as arbuscule-like, holding open the question of whether a true resource exchange is occurring. That proof remains the work ahead.
The stakes of that proof are considerable. Mosses are close relatives of the earliest plants to colonize land some 470 million years ago, and fungal partnerships are already thought to have been essential to that ancient greening of the continents. If mosses have been hosting these relationships all along — undetected, misunderstood — the evolutionary story of how life moved from water to land may need revision. Closer to the present, the finding raises the possibility that specific fungi could one day inform efforts to restore the biological soil crusts now threatened by warming, drought, and human disturbance. For now, the discovery stands as a reminder that the most consequential relationships are sometimes the ones growing quietly, unnoticed, beneath our feet.
Beneath the surface of some of Earth's harshest deserts lies a discovery that upends a century of botanical thinking. Researchers at UC Riverside have found fungi living inside desert moss tissues—a relationship scientists believed impossible. The finding, published in New Phytologist, suggests that mosses, long treated as evolutionary loners, may have been harboring fungal partners all along.
Desert soil is not barren. In the Mojave and Sonoran deserts, where temperatures climb above 100 degrees Fahrenheit, the ground itself forms a living crust. This thin, dark layer contains mosses, fungi, bacteria, algae, and microscopic animals woven together in a fragile ecosystem. The mosses are the survivors of this world. They can dry out until they appear dead, then revive after rain. They cling to bare rock, endure scorching heat, and persist through months without water. Scientists have even wondered whether such resilient plants might one day help sustain life in extreme environments beyond Earth.
But mosses were thought to achieve this durability alone. Unlike the vast majority of land plants—more than 85 percent—mosses were believed to lack partnerships with fungi. Most flowering plants, trees, and crops form relationships with arbuscular mycorrhizal fungi, or AMF, which burrow into roots and exchange nutrients for sugars produced by photosynthesis. Mosses, lacking true roots, seemed exempt from this bargain. For decades, the scientific consensus held that all 10,000 known moss species lived without fungal help.
Kian Kelly, a doctoral researcher at UC Riverside, decided to test that assumption. He collected mosses from the Mojave and Sonoran deserts, searching through extreme heat for specimens from biological soil crusts—the living skin of drylands that stabilizes loose soil and supports entire ecosystems. These crusts are fragile; a single footprint can damage them for decades. Kelly wanted to know whether mosses from different climates harbored different fungal communities. The question mattered because drylands are expanding globally, and if certain fungi help mosses tolerate heat and aridity, they could shape how desert ecosystems respond to climate change.
In the laboratory, Kelly ground up moss samples and searched for fungal DNA. The results revealed fungi inside the tissues. More surprising still, the fungi included mycorrhizal species—organisms known to depend on plant partners. These were not simply soil organisms clinging to the moss surface. The fungal communities inside desert mosses differed from those in nearby soil and from those found in mosses collected from less severe environments. The pattern suggested something more selective than contamination: a relationship shaped by the demands of extreme climate.
To move beyond DNA evidence, Kelly stained moss tissue with a blue dye that binds to fungi and examined the samples under a microscope. Inside the moss cells, he saw branching fungal structures. They resembled arbuscules—the tree-like formations that mycorrhizal fungi typically build inside plant roots—but mosses have no true roots. These structures appeared in leaves instead. The researchers call them arbuscule-like, a careful designation that acknowledges the similarity while stopping short of claiming a proven symbiosis. Proving that mosses and fungi actually exchange resources remains the next step.
The implications extend far beyond desert ecology. Mosses belong to an ancient plant lineage and are close relatives of some of the earliest plants that colonized land roughly 470 million years ago. When plants first left water, they faced enormous challenges: obtaining nutrients, avoiding desiccation, surviving without aquatic support. Fungal partners may have been crucial to overcoming these barriers. Evidence of plant-fungal associations appears deep in the fossil record, and many scientists view these partnerships as central to the greening of Earth's continents. If mosses can host mycorrhizal fungi in ways scientists previously overlooked, it could reshape understanding of how early plant-fungal relationships evolved.
The discovery may also offer new paths for restoring damaged drylands. Biological soil crusts are increasingly threatened by warming, drought, grazing, and human disturbance. Recovery takes years or decades. For now, the study does not prove that fungi help mosses survive extreme conditions. It does reveal a hidden association that scientists did not expect. As Kelly reflected on his work in the desert heat, he noted that the biggest surprises often grow quietly, unnoticed, beneath our feet.
Citações Notáveis
We suspect that certain fungi are more helpful for surviving hotter, drier climates— Kian Kelly, UC Riverside doctoral researcher
As soon as I saw that, I knew we had something really interesting— Kian Kelly, describing the moment he observed fungal structures under the microscope
A Conversa do Hearth Outra perspectiva sobre a história
Why did scientists assume mosses didn't need fungi in the first place?
Mosses lack true roots, which is where fungi typically live in other plants. Without roots, the logic went, there was no place for the partnership to happen. It was a reasonable assumption based on what we knew about how fungi work elsewhere.
But you found fungi anyway. Inside the leaves?
Yes. We found arbuscule-like structures in leaf cells—branching formations that look like the nutrient-exchange sites fungi build in plant roots. The fungi were selective too, not just random soil contamination. Desert mosses had different fungal communities than mosses from wetter places.
What does that selectivity tell you?
It suggests the fungi are actually living there, adapted to the conditions. If they were just stuck to the surface, we'd expect the fungal DNA inside the moss to match the soil around it. Instead, it was different. That pattern points to a real relationship.
Can you prove the fungi are actually helping the moss?
Not yet. We can show they're there and that they look like they're exchanging nutrients, but we haven't demonstrated the actual resource trade. That's the next phase of the work.
Why does this matter for understanding early plant evolution?
When plants first moved onto land 470 million years ago, they faced impossible conditions. Fungi may have been the key to survival. If mosses—which are close to those ancient plants—can partner with fungi in ways we didn't know about, it changes how we think about that critical transition.
And for deserts today?
Biological soil crusts are being destroyed by climate change and human activity. If we understand which fungi help mosses survive extreme heat and dryness, we might be able to use that knowledge to restore damaged drylands more effectively.