This Plant Survived for 400 Million Years. Then It Met Us - Climate Change - Haaretz

This Plant Survived for 400 Million Years. Then It Met Us - Climate Change - Haaretz.com

High on the Tibetan Plateau is the world’s oldest plant, and it has evolutionary superpowers. Takakia is a moss that split off from other early mosses almost 400 million years ago – note that terrestrial plants only began to emerge about half a billion years ago – and as the plateau rose because of plate tectonics, in Tibet it evolved resistance to extreme cold and altitude. The environmental stresses it endured led Takakia to develop a record number of fast-evolving genes among plants, a team explained last week in the journal Cell.

Over the eons, Takakia weathered at least four mass extinctions. It survived the geologically violent formation of the Himalayas on which it now perches. It is able to survive under snow for eight months of the year and to withstand deadly ultraviolet radiation. But it has become rare and, after all this time, may face final extinction because of the extreme and rapid climate change in its habitat.

It bears adding that until now, doubts had persisted as to whether Takakia was a moss, because it also has some features more typical of liverwort or algae. Its true identity was elucidated by the genetic analysis now reported by the team, which determined that it is actually a moss and that the ancestral Takakia split from its mossy brethren about 390 million years ago. Two species of it have survived to this day: T. ceratophylla and T. lepidozioides.

Takakia lepidozioides growing on a damp slope above Takakia Lake, Haida Gwaii.Credit: Stu Crawford

The only place both species still survive is Tibet, above 4,000 meters (13,120 feet), but each also has some representatives in Alaska and British Columbia, Japan and a few spots in Southeast Asia. The reason for its present spotty presence is unclear, but back in the day it probably had a much wider distribution.

Technically, the paper dwells on the genetic properties that enabled Takakia to become one of the older “living fossils” on Earth (certainly jellyfish, and likely sharks, may be even older).

The team describe fossil Takakia from Mongolia 165 million years ago that shows the plant already had its distinct morphology by then. However, the moss evolved its unique resilience to deadly ultraviolet and cold only recently, everything being relative. Here, that means after the Himalayas on which they perch today began to emerge and rise skyward. Geologists estimate that this was about 60 to 40 million years ago, as the Indian subcontinent collided with the Eurasian plate.

Some populations of this primordial plant also exist at lower altitudes in a few habitats around the world. The ones in Tibet were discovered in 2005 at altitudes greater than 4,000 meters by co-author Prof. Xuedong Li.

Globally vulnerable

How unique is this creature? Very. Its hardiness aside, externally Takakia is like the early terrestrial invaders of the land, seemingly unchanged over hundreds of millions of years, according to a Nature article on the plant. Its leaves don’t have the characteristics of modern plants on either their bottom or sun-facing top.

While they don’t have stomata (the pores through which plants have been breathing ever since the ancestral plant colonized dry land), it isn’t that Takakia predates stomata – it’s that it secondarily lost the genes at some point, research indicates.

Anyway, how did this wee plant, mere millimeters in size per individual, achieve mega-survival distinctions? The team suggests that as the Himalayas rapidly emerged, the only survivors would have been the individuals that mutated fast in multiple characteristics to adapt.

Takakia ceratophylla. While Takakia can be grown in the lab, it’s not much of a comfort.Credit: HelloitsFaith

Its story is a remarkable one but unfortunately, like its fellow living fossil the shark, Takakia is in trouble, the researchers warn – and it’s for the same reason: our destructiveness. On the Tibetan Plateau, the Takakia population is declining by 1.6 percent a year, double the pace of decline in other mosses there. It is now listed by the International Union for Conservation of Nature’s Red List of Threatened Species as globally vulnerable, though the state of its populations elsewhere remain to be investigated. If it’s any comfort, another living fossil, the jellyfish, seems pretty okay in our changing seas, so far at least.

Why is this happening? Because what survives of Takakia has become highly specialized and because of the sheer speed of the anthropogenic changes, apparently. The Tibetan Plateau has become a climate change hot spot, with a temperature increase above 4,000 meters of almost half a degree Celsius a year between 2010 and 2021, according to co-author Ralf Reski. That is enormous.

It evolved to survive bitter cold on the heights, not being baked. It evolved over millions upon millions of years to survive the cold and radiation, but in Tibet its habitat is radically changing within mere years. Less specialized moss are still clinging on and some plants there are actually enjoying the weather, but Takakia populations on the plateau are shrinking.

“Decrease in Takakia abundance was significantly correlated with increase in maximal growing season temperature,” the researchers write. Testing a possible contribution by change in nutrients showed that, actually, the only parameter shaping the decline of the species was atmospheric warming. In the future, the team means to study Takakia beyond Tibet.

Meanwhile, have they proved that climate change is the only reason for Takakia’s decline? The Nature coverage of the report notes the opinion of bryologist Lalita Calabria at the Evergreen State College in Olympia, Washington: that bryophytes, which includes mosses, are vulnerable to other environmental changes such as air quality and humidity – which are certainly not improving – and they’re doing so fast. Not a corner of the planet is free of pollution.

It bears adding regarding potential extinction that Takakia can be grown in the lab. It’s not much of a comfort.