Takakia in Tibet: the adaptations of a moss at high altitude

The moss Takakia lepidozioides, a rare plant from the Tibetan plateau, has embarked on a remarkable evolutionary journey spanning millions of years to adapt to high altitude. In a study published in Cell, an international research consortium led by scientists from the University of Freiburg and the Capital Normal University of Beijing reconstructed Takakia evolution and revealed the genetic traits associated with its adaptation to one of the most unforgiving environments on Earth. Moreover, the study documents how climate change has dramatically altered the natural habitat of this species within just a few years, threatening it with extinction.

Commencing 65 million years ago, the Himalaya-Tibetan plateau was uplifted by the India-Asian collision, reaching above 4000 m elevation. This spectacular geological event has forged one of the most hostile environments on the planet, characterized by the persistence over months of freezing temperatures and exposition to high levels of solar radiations. Yet, the Tibetan plateau is also known as a biodiversity hotspot. Understanding how organisms adapt to extreme environments is therefore a central issue in evolutionary biology.

The genus Takakia comprises only two moss species, both being endemic to the Tibetan plateau. There, populations of the species Takakia lepidozioides were discovered in 2005 and have been studied since both in their natural environment and in the laboratory. Through comprehensive genome sequencing, the scientific consortium of 61 researchers including Hugues Renault from IBMP established that Takakia branched off from all other mosses about 390 million years ago, making it one of the oldest living plant species. Genome survey also disclosed an unusually high number of genes evolving rapidly under positive selection. And yet, based on fossil records, researchers were able to show that Takakia morphology remained unchanged since at least 165 million years.

On the Tibetan plateau, Takakia lepidozioides experiences eight months buried under snow, followed by relentless exposure to intense solar radiation throughout the rest of the year. The study shows that Takakia has acquired genetic traits, notably linked to metabolic protection against UV and free radicals, in order to adapt and survive in these extreme conditions. Furthermore, the study captured the dynamics of these genetic adaptations, which gradually unfolded after the uplift of the Tibetan Plateau. However, despite its demonstrated ability to adapt to major environmental changes in the course of its evolution, Takakia is now facing a rapid change of its habitat, with temperature rising by 0.43°C every year. While some plant species benefit from these changes, Takakia lepidozioidespopulations exhibit alarming decline, showcasing the speed by which climate change threatens some species living in vulnerable ecosystems.