The koala genome shows how adorable marsupial lives on eucalyptus leaves

Before tackling science, let's all admit that we want a koala. So cute!

The koala defies the kangaroo as the most emblematic Australian marsupial. It is a very special, spectacularly specialized animal, living in eucalyptus and surviving almost entirely on their leaves, which are very toxic to most organisms.

But not about any eucalyptus: There are about 600 species of eucalyptus and koalas There are only 120 species, of which only 20 species provide most of the koala diet. And koalas are very selective about their green leaves, preferring those rich in nutrients and water and stopping to bury their adorable faces of Yoda in the leaves for a big sniff before nibbling.

So they are certainly not generalists.

"You talk about a niche in a niche," says Rebecca Johnson, director of the Australian Museum Research Institute.

Johnson and dozens of Australian colleagues published Monday the complete koala genome in the journal Nature Genetics.

Biological instructions for making a koala illuminate how this animal survives. One finding is that the koala has an unusual number of genes that code for enzymes that can break down toxins in the leaves.

Genetic information could prove crucial for the conservation of koalas, species threatened by disease and habitat fragmentation. An immediate goal for conservationists would be to use genetic data to improve vaccines already deployed to prevent the spread of chlamydia, a bacterium that causes blindness and urinary tract inflammation in koalas, said Katherine Belov, co-author of the study. of comparative genomics

They are great sleepers. A koala sleeps about 14 hours a day. The rest of his day is spent eating and resting. He moves, on average, four minutes a day.

Koalas, says Johnson, "are essentially wombats who decided to go to the trees." They had to face less competition for food in the trees as they evolved.

Koalas endured a death about 30,000 years ago for unknown reasons and then suffered another blow when Europeans arrived in Australia more than two centuries ago.

Koalas live all along the east coast of Australia, where most of the human population is found, but they form two distinct genetic populations. In the north, they are genetically diverse but their numbers are decreasing due to urbanization and deforestation.

In the south, they are everywhere and, in many cases, they die of hunger by baring trees. But they descend from a small founding population, probably established from captive animals two centuries ago, after European settlers had eliminated the wild population, said Belov. They can all come down from about twenty animals, she says.

"When genetic diversity is very low, animals become essentially immunological clones, so any change in disease, temperature change, climate change can potentially affect the entire population," Belov said in Washington. To post. "It can be said that there are many animals but that does not mean that there is a genetically healthy population."

A niche existence, especially consanguineous, is precarious on a planet in rapid evolution knowing global warming and direct impacts colossal human civilization.

Koalas experienced rapid population declines around the same time that much of the Australian megafauna disappeared more than 30,000 years ago. Human predation seems unlikely, Johnson said. According to traditional knowledge of the Aborigines, koalas were considered sacred in many communities, Johnson said. Archaeologists have not found koala remains in human mounds, she said.

It is unclear what led to the collapse of the prehistoric population

"It is very likely that there will be large-scale environmental changes.] Read more:

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