The largest plant in the world is an ancient self-cloning sea grass

Shark Bay, an Australian World Heritage Area, serves as home to various animals that feed on its thriving sea grass. Turns out that sea grass called Poseidon’s ribbon weed, or Posidonia australis, is a single ancient plant that’s been cloning itself for the past 4,500 years. Researchers from The University of Western Australia and Flinders University studied samples of the organism taken from across the bay and generated a DNA fingerprint with 18,000 genetic markers. What they found was that the sea grass stretching across 180 kilometers (112 miles) — the size of Cincinnati, as The New York Times notes — of Shark Bay is just a single plant. 

Senior author Dr. Elizabeth Sinclair said they’re often asked how many plants grow in sea grass meadows. For Shark Bay, lead author and UWA student Jane Edgeloe said: “The answer blew us away — there was just one! That’s it, just one plant has expanded over 180km in Shark Bay, making it the largest known plant on Earth.”

The Posidonia apparently clones itself by producing new shoots growing out of its root system. It doesn’t reproduce sexually, because it’s most likely unable to: The organism has a condition called polyploidy, which means it inherited 100 percent of each parent’s genome instead of just 50 percent from each. Since polyploidy often results in sterility, cloning might be the only way for the Shark Bay Posidonia to proliferate. 

Sinclair said its polyploidy might have also made it more resilient than usual, though. It could have given the organism the “ability to cope with a broad range of conditions, which is a great thing in climate change.” It remains to be seen whether the Shark Bay Posidonia will continue to thrive in the face of modern climate change, but the researchers may find out soon enough. They’ve set up a set of experiments to figure out how it survives in environments with variable conditions that include a wide range of temperatures and salinities, as well as extreme brightness and darkness.

You can read the group’s paper in Proceedings of the Royal Society B.