A High Altitude Plant Facing Climate Change in Tibet

Environmental & Science Education, STEM, Nature, Sustainability, Global Change, Global Climate Change, Biological Evolution, History of Science, Nature of Science

Ed Hessler

 

Context: The discussion of the following scientific paper is the story scientists are piecing together on a moss. The moss, genus Takakia has found a place in the natural world for 400 million years, roughly the geological period known as the Devonian. Evidence suggests that it is in danger of extinction Tibetan Plateau to which it has been famously adapted to what the environment has on offer: cold and harmful radiation from the sun. And that story began roughly 50 million years ago when India pushed into into Asia causing the uplift. In 2005 the two exisiting species were discovered by a survey team. The team set up study plots and since then have returned twice a year to collect environmental data. The outlook for its survival there strongly suggests that this highly specialized plant will disappear as the globe continues rapidly changing temperature increases. It may not have enough evolutionary time for further adaptations and adjustments.

A short sentence from a paper I just read (lightly) caught my attention. "Following nearly 400 million years of evolution and resilience, this species is now facing extinction."

The species is Takakia lepidozioides, a moss adapted to live in high altitudes, 4000 m plus (~13,000 feet).

The paper "Adaptive evolution of the enigmatic Takakia now facing climate change in Tibet" (PDF - Don't be put off by its length.) was published August 9, 2023 in the journal Cell. The research involved multiple specialties and authors with a key to their contributions which you can view by clicking on the authors. This is not as cumbersome as it might seem since the author key (digits) is used multiple times.

There is a list of highlights, a graphical abstract, a summary and keywords. I included the highlights so I could link to possible problematic technical vocabulary and ideas. And don't forget to use Google when in doubt of a technical word or concept.

Highlights:

• •
  Steepest temperature increase at 4 km elevation threatens highly adapted moss species
• •
  Sequenced genome with highest number of fast-evolving genes under positive selection. (There are two types of natural selection in biological evolution: Positive (Darwinian) selection promotes the spread of beneficial alleles, and negative (or purifying) selection hinders the spread of deleterious alleles. See here.
• •
  Adaptation to severe UV-B radiation and freezing likely evolved at high altitudes
• •
  Morphological peculiarities of Takakia plants likely evolved earlier than 165 mya
• There are probably several points which will attract your attention. Here are 3 that caught mine.
• 1. Takakia is a "sister to all other mosses, including Sphagnum...despite their morphological dissimilarities."
• 2. "Takakia lacks rhizoids, ,,, Instead of rhizoids that attach plants to the soil matrix, Takakia  evolved a morphology that is not known from other mosses." (Oxford Languages Dictionary defines matrix as "an environment or material in which something develops; a surrounding medium or structure.")
• 3. Stomata were one of the first developmental innovations of land plants, at about 400 mya (million years ago).  However, Takakia lacks stomata." 
• From the Summary:
• In short the authors documented "the steepest temperature increase (2010–2021) on record at altitudes of above 4,000 m, triggering a decline of the relictual and highly adapted moss Talakia." The summary is short.
  
  
  
• The modern origin of protective traits in Takakia. 
• Whereas Takakia evolved characteristic morphological features before 65 mya, the duplication and divergence of genes involved in stress protection occurred mainly during the uplift of the Himalayas, namely from 50 mya to the present. This period is characterized by a sharp increase in harmful UV-B radiation and a sharp drop in temperature, both caused by the uplift of the region." Whereas 
  
  Takakia evolved characteristic morphological features before 65 mya, the duplication and divergence of genes involved in stress protection occurred mainly during the uplift of the Himalayas, namely from 50 mya to the present. This period is characterized by a sharp increase in harmful UV-B radiation and a sharp drop in temperature, both caused by the uplift of the region. Whereas Takakia evolved characteristic morphological features before 65 mya, the duplication and divergence of genes involved in stress protection occurred mainly during the uplift of the Himalayas, namely from 50 mya to the present. This period is characterized by a sharp increase in harmful UV-B radiation and a sharp drop in temperature, both caused by the uplift of the region. The uplift of the Himalayas has caused the annual average temperature in the area of our experimental site to drop from 27°C (50 mya) to about 5°C at present, forcing Takakia  to evolve enhanced freezing tolerance."  (This sounds somewhat intentional which I doubt is the intention of the researchers. I prefer the idea of natural selection.)
• This is a technical scientific paper but the paper's discussion, a couple of short videos and parts of the discussion are accessible and downright fascinating.  Every day we are learning more about the reach of global climate change and its effects on the large, the small, the deep, the high, the widespread and the isolated.
• The authors conclude with a short section on the limitations of the study.