Study: Lichens Thrived Post-Mass Extinction Event

(CN) – When one door closes, another one opens. This is what happened 66 million years ago when an asteroid collided with Earth, decimating ecosystems and most famously, the dinosaurs. 

Scientist Thorston Lumbsch, who grew up fascinated by lichens, wanted to know how these symbiotes fared in the wake of mass extinction, how they were affected by dramatic climate change, and why they diversified so much after the disaster. What he found is nothing short of astounding.

 “If you look at Earth from the moon, you can see the full picture, but you can’t see all the details,” Lumbsch said, drawing a parallel to the way lichens change over time.

A recent study conducted by researchers from The Field Museum in Chicago and published Friday in the journal Scientific Reports used molecular data to see which groups of lichens increased in divergency after the mass extinction event. 

Lead author Jen-Pan Huang on a lichen-covered rock in Taiwan. (JP Huang)

When the mass extinction occurred, substantial plant life died out due to inadequate sunlight and low temperatures. It was assumed that lichens were affected in the same way, but new information shows they were astonishingly able to grow and reproduce. Macrolichen filled the niches of the deceased plants and diversified, growing complex leaf-like structures and intricate compositions. 

Lichens are unique because they are two different organisms forming one body in order to survive. The algae create energy through photosynthesis and the fungi decompose surrounding materials.

“Symbiotic systems are very sensitive to changes in their environments,” Lumbsch said. “[They] react very quickly to changes and when they are in stressful situations, the two organisms try to figure out how to survive.”

The study found that the macrolichen created a greenhouse for algae to perform photosynthesis, which is why they were able to thrive.

These findings show us that symbiotes like lichen are some of the first indicators of environmental changes.

“[We can] use symbiotic systems as canaries in a coal mine…when something serious needs to be addressed,” Lumbsch said.

In the 50s and 60s when air pollution was at its height, “lichens disappeared [because] they were sensitive to climate change,” the same way corals show signs of bleaching and even death as ocean temperatures rise. 

Lumbsch warns that these symbiotic systems are among the “first warning signs that we have to be careful not to change much more and cause a mass extinction.” 

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