In Shark Bay on the west coast of Australia, there is a vast seagrass meadow.
They grow in shallow waters, and through the sparkling crystal clear waters, you can see soft and flowing seagrass leaves stretching out in the water.
The meadow covers an area of 200 square kilometers, three times the size of Manhattan Island in New York, and is probably the most lush seagrass on the West Coast.
There must be a lot of seagrass here, right?
Marine biologists at the University of Western Australia think so.
They wanted to know that there are several types of seagrass in this meadow, and if there is marine pollution in the future, they can plant corresponding seagrass to fill the gap.
To know how many plant species there are in the meadow, you have to test their DNA.
The UWA team dives into Shark Bay to take samples from 10 seagrass piles and compare 18,000 genetic sites.
These seagrass piles are located in various corners of Shark Bay, far apart, and they can roughly estimate the condition of the entire meadow.
However, the final test results surprised the scientists:
Why is the DNA exactly the same for all seaweed samples!?
The only seagrass they found was australian neptune grass, and they didn't have any genetic differences from each other.
This means that this 200 square kilometre seagrass meadow is made up entirely of one Australian neptune grass, with only one plant.
"We thought to ourselves, what the hell is going on?" Ecologist Martin Breed exclaimed, "Really, very confused." ”
"Although, we thought the seagrass here was not normal at the beginning. They rarely flower, do not produce seeds, and the signs of reproductive activity are not obvious. ”
After careful study, scientists discovered that this Australian neptune grass is bred from rhizomes.
Seagrass has two ways of reproduction, one is sexual reproduction, through flowering and fruiting, combining its genes with those of other seagrasses.
The other is asexual reproduction, where seaweed extends its own rhizomes, growing new seaweeds on the rhizomes, constantly cloning itself outward.
Doctoral student Jane Edgeloe said they found seaweed flowers but did not see the fruit, suggesting that the Australian neptune may not be sexually reproducible and can only be cloned.
"This 200-square-kilometer seagrass meadow should have grown from a single, colonized seedling."
"The plant spreads like a meadow, providing a comfortable habitat for marine life such as turtles, dolphins, dugongs, crabs and fish."
The rhizome of the Australian neptune grass can grow up to 35 centimeters per year, and at this rate, scientists estimate that the plant has been growing for 4500 years.
It's not surprising that seagrasses have grown for so long, it's strange why asexually reproducing seagrasses can grow for so long.
The disadvantages of asexual reproduction are very obvious, because the genes of the plant remain unchanged, its adaptability to the external environment is very poor, and the slightest wind and sea movement will die.
Shark Bay's environment is also particularly harsh (for seagrass), it has twice the salt content of other seas, low nutrient content, and a huge temperature difference between seawater and can change from 15 degrees to 30 degrees. The light of the day is also very intense, causing it survival pressure.
Even if the conditions are so harsh, this Australian neptune grass is still alive and well,
In the summer of 2010 and 2011, when a third of the seagrasses died during severe heat waves off the coast of Western Australia, the seagrass survived tenaciously and is now recovering very well.
It is not simply "grass strong", the answer is still in the genes.
Dr Elizabeth Sinclair said they found neptune grass in Australia as a hybrid polyploidy plant.
One of its parents is an Australian neptune and the other is a close seaweed. Usually, sexually reproducing plants get half of their chromosomes from their parents, but this "strong grass" means that it wants them all.
"It doesn't get half of the chromosomes from the mother and half from the father. It preserves all of their genes. Dr. Sinclair said.
"So it has twice as many chromosomes as other Australian neptune grasses, not 20, but 40."
Doing so doubles the plant's genetic diversity and enhances its ability to cope with extreme environments. ”
This explanation is reasonable, but there are too many extreme environments in 4500 years, and one more set of chromosomes may not be enough.
Scientists speculate that the Australian neptune may have a small number of somatic mutations that make it more resistant to salt and heat.
Their findings were published in the recent Proceedings of the Royal Society, Series B.
It tells the story of the grass of this seaweed:
About 20,000 years ago, at the end of the last ice age, Shark Bay was still a piece of land.
As the ice sheet melted, the ocean rose, and by 8,000 years ago, it was submerged by the sea and turned into a shallow bay.
Soon after that, many seagrass plants came here to grow,
4500 years ago, an inconspicuous hybrid seed fell here and began a legendary life.
At that time, Shark Bay was almost all ordinary diploid plants, some sexually reproducing and some asexual reproduction.
There are many genes for sexual reproduction, but slowly, and asexual reproduction is fast but less genetic.
And that magical hybrid seaweed, precisely because it can only reproduce asexually, has the advantage.
Relying on a slightly mutated hybrid multiploid identity, Seagrass gradually occupies the bay, defeats its opponents, and becomes the behemoth it is today.
Professor Kathryn McMahon of Edith Cowan University was not involved in the study, but she is a seagrass expert, and based on information provided by the University of Western Australia, she found the discovery stunning.
Genetic studies of other seagrass species estimate that these plants can survive for 2,000 to 100,000 years, and this Australian neptune is in the normal range.
"Seagrasses grow in a variety of ways, using a variety of ways to prolong life. For example, growing in nutrient-rich seas, or developing into places where there is less pressure to compete. This characteristic means that they can live a long time as long as they are born in the right place. ”
Growing to nearly 200 square kilometers, she thinks is also reasonable, because seagrass is not growing in a single line, but the entire outer circle is expanding.
"Marine plants have grown very fast, and with each seagrass branching out and growing for 4,500 years, it is not surprising that it has become so big now."
Scientists confirm that this seagrass is currently the largest single plant found in the world.
Previously, the name "Largest Plant" belonged to the poplar tree in Utah, USA, called "Pandaoklon Tree".
It covers an area of 0.4 square kilometers and consists of 47,000 poplar trees, which looks like a beautiful but ordinary poplar forest.
But in fact, pando clone trees also grow new trees by expanding the root system. All the seemingly independent trees all came from a single root system, and it grew at least 80,000 years to grow so much now.
Although in terms of weight, it is the Pandalon tree that is larger, but in terms of area it is clear that the Australian neptune grass has won the title of "the largest in the world".
The Australian poseidon doesn't have a name yet, and scientists are busy experimenting in Shark Bay to find more secrets to its adaptations.
In the future, maybe people will give it a great nickname,
From a small seed to what it is today, it is worth remembering by the world...