Dinokiller ": Lichen as winner

Symbiotic communities benefited from mass extinction 66 million years ago

Lichen was apparently one of the winners of the "Dinokiller" strike. © Jen-Pan Huang
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Beneficiaries of the disaster: Not only mushrooms, but also some lichens evidently emerged as the winners of the mass extinction 66 million years ago. Analyzes suggest that larger lichens with leaf-like structures in particular benefited from the "dinokiller" impact. After this disastrous event for a large part of the living beings, they experienced a veritable heyday - and were able to occupy ecological niches that had been freed by extinct plants.

Some 66 million years ago, one of the most famous catastrophes in Earth's history occurred: when an asteroid hit the planet at the time, it not only sealed the fate of the dinosaurs. The "dinokiller" impact triggered a mass extinction, which also early birds, insects and a variety of other animals and plants fell victim.

However, there were also profiteers of this disaster: fossil records indicate that mushrooms experienced a heyday after the event. Unlike many plants, they did not mind the years of winter and winter impact on the impact because they do not photosynthesize and therefore do not need sunlight to survive.

Winner or loser?

Researchers led by Jen-Pang Huang at the Field Museum in Chicago have wondered what the asteroid impact of 66 million years ago was for lichens. They are a symbiotic partnership of fungi and photosynthetic organisms such as algae or cyanobacteria - making them the winners and losers of the disaster, as the team explains.

"Our initial hypothesis was that the lichens were also negatively affected. Because they contain ingredients that need light, "says Huang. But is this assumption true? To find out, the scientists analyzed DNA sequences from representatives of the two most important subclasses of lichen formers: Lecanoromycetidae and Ostropomycetidae. display

Accelerated diversification

Using a computer program, they were able to draw conclusions on the genealogical tree of the lichens and to estimate when the individual lines had to split off from each other and the lichen groups we know today. These findings then combined them with the few fossil finds that lichen gives.

The evaluations revealed that while some lichen groups apparently had little change and some even died out after the impact, others profited from the disaster. "Our results show accelerated diversification in three families of lichen-forming fungi: Cladoniaceae, Parmeliaceae and Peltigeraceae, " the researchers report. "These changes in diversification rates were most likely related to the mass extinction 66 million years ago."

Lichen replaced plants

The now identified winning families of the "Dinokiller" impact are mainly composed of so-called macroframes, which develop complex, leaf-like structures. "Some lichens form structures that look like plant leaves - and it was these lichens that boomed 66 million years ago. They filled ecological niches that had previously been occupied by plants, "explains Huang.

The reason why these lichens benefited from the new environmental conditions and created new species is something the researchers can only speculate on. "The different reactions to historical events, such as the asteroid impact, may be related to the development of certain characteristics. However, based on currently available data, we are unable to draw more accurate conclusions in this regard, "they conclude. (Scientific Reports, 2019; doi: 10.1038 / s41598-019-44881-1)

Source: Field Museum

- Daniel Albat