World's Oldest Moss May Not Survive Humans

A rare moss called Takakia has adapted over hundreds of millions of years to survive the extremes of life on the cliffs of the Tibetan Plateau. Now, a team of researchers who have been studying the moss for nearly a decade says that despite being one of the fastest-evolving species ever studied, Takakia may not be adapting quickly enough to survive climate change.

The genus Takakia includes just two species, both of which are found only on the Tibetan Plateau—an area the researchers refer to as the “roof of the world.”

Professor Dr. Xuedong Li, one of the two first authors of the study, discovered populations of Takakia at an altitude of over 13,000 feet (4,000 meters) in 2005. The team has been studying the moss on-site and in the lab ever since.

Life on the Tibetan Plateau isn't easy. Takakia is buried under snow for eight months of the year and exposed to high levels of UV radiation when it emerges from its snowy cover.

Takakia has been evolving in this location for over 65 million years, ever since the region was formed by continental drift, making the habitat increasingly extreme.

“These geological time records help us to trace the gradual adaptation to a life at high altitudes in the Takakia genome,” explains Dr. Ralf Reski from the University of Freiburg, who led the team along with Dr. Yikun He from the Capital Normal University in China. The latest research looked at how the moss has been able how to develop the ability to survive life-threatening extremes.

In the study, they also document how climate change has significantly altered the moss' habitat within just a few years.

The team was surprised to find Takakia's shape in 165 million-year-old fossils from Inner Mongolia, revealing that genetic changes affecting shape evolved more than 165 million years ago under wildly different conditions.

“Although the Takakia genome is evolving so rapidly, the morphology has not changed recognisably for more than 165 million years," says Reski. "This makes Takakia a true living fossil. This apparent contrast between unchanged shape and rapidly changing genome is a scientific challenge for evolutionary biologists."

All told, Takakia is some 390 million years old—and is host to the fastest evolving genes ever discovered.

“We have now been able to prove that Takakia is a moss that separated from the other mosses 390 million years ago, shortly after the emergence of the first land plants. We were surprised to find that Takakia has the highest known number of fast-evolving genes under positive selection”, says He.

But despite having hundreds of millions of years to evolve to increasingly extreme changes, climate change may put an end to the little moss that could.

Since they began taking measurements of Takakia's habitat in 2010, the researchers describe an average temperature increase of almost half a degree Celsius per year. Meanwhile, the glacier near the sample sites is receding at an alarming pace—around 130 feet (50 meters) per year.

The researchers note that Takakia populations have become significantly smaller over the study period. Between 2010 and 2021, the coverage of Takakia populations decreased by 1.6% annually, faster than that of four local common mosses—a trend they expect to continue.

“Our study shows how valuable Takakia is in tracing the evolution of land plants. The population decline we found is frightening,” He says. “Fortunately, knowing that the plant is threatened by extinction also gives us a chance to protect it, for example, by growing it in the lab,” adds Hu.

“Takakia has seen the dinosaurs come and go. It has seen us humans coming," Reski concludes. "Now we can learn something about resilience and extinction from this tiny moss."