Australian researchers have located what is believed to be the largest plant on Earth and they estimate it to be at least 4,500 years old.
The ancient and incredibly resilient seagrass that stretches for 180 km has been located by researchers from the University of Western Australia and Flinders University.
The discovery of the unique Posidonia australis seagrass plant or ‘clone’ in the shallow, sunny waters of WA’s Shark Bay World Heritage Area is detailed in a new study published in Proceedings of the Royal Society B.
Lead author, evolutionary biologist Dr. Elizabeth Sinclair of the UWA School of Biological Sciences and the UWA Institute of Oceans, explains that the project began when researchers first wanted to understand how genetically diverse the seagrass in Shark Bay was and what plants should be collected for the seagrass. restoration.
“We are often asked how many different plants grow in seagrass beds and this time we used genetic tools to answer them,” says Dr Sinclair.
UWA student researcher Jane Edgeloe, lead author of the study, says the team sampled seagrass shoots from the variable environments of Shark Bay and generated a “fingerprint” using of 18,000 genetic markers.
“The answer blew us away – there was only one.” said Mrs. Edgeloe. “That’s it, a single plant has spanned 180 km in Shark Bay, making it the largest known plant on Earth.
“The existing 200 km2 ribbon weed meadows appear to have developed from a single colonizing seedling.
Flinders University ecologist Dr. Martin Breed, co-author, was part of the research group. He says the study presents a real ecological conundrum.
“This single plant may actually be sterile; it has no sex. How it has survived and thrived for so long is truly puzzling. Plants that have no sex also tend to have reduced genetic diversity, they normally need to deal with environmental changes,” says Dr Breed, from Flinders University’s College of Science and Engineering.
“Our seagrass has also seen its fair share of environmental changes. Even today, it experiences a huge range of average temperatures; from 17 to 30°C. Salinities ranging from normal sea water to double. darkness to extremely high light conditions.These conditions would usually be very stressful for plants, but it seems to continue.
” How is it ? Well, we feel that its genes are very well adapted to its local, but variable environment, and that it also has subtle genetic differences across its range that help it cope with local conditions,” says Dr. Breed. .
Dr. Sinclair said what makes this seagrass plant unique from other large seagrass clones, other than its huge size, is that it has twice as many chromosomes as its oceanic relatives, which means that it is polyploid.
“Whole genome duplication by polyploidy – doubling the number of chromosomes – occurs when diploid ‘parent’ plants hybridize. The new plant contains 100% of each parent’s genome, instead of sharing the usual 50%,” explains Dr. Sinclair.
“Polyploid plants often reside in places with extreme environmental conditions, are often barren, but can continue to grow if left undisturbed, and this giant seagrass does just that.
“Even without successful flowering and seed set, it seems to be really resilient, experiencing a wide range of temperatures and salinities as well as extremely high light conditions, which together would generally be very stressful for most plants.”
Researchers have now set up a series of experiments at Shark Bay to understand how this plant survives and thrives in such variable conditions.
Seagrass doubles its chances in ultimate breeding strategy
Jane M. Edgeloe et al, Extensive polyploid clonality was a successful strategy for seagrass growth in a newly submerged environment, Proceedings of the Royal Society B: Biological Sciences (2022). DOI: 10.1098/rspb.2022.0538
Provided by Flinders University
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