World’s largest organism found in Australia

It sounds like a science fiction novel: Two closely related species hybridize and create a superorganism that seems unstoppable. In Western Australia's Shark Bay, a single hybrid plant has extended its reach across more than 180 kilometers, researchers say.

Two years ago, scientists discovered a clone of a plant that had 40 chromosomes instead of the usual 20. They think half of the chromosomes are from the ribbon weed.

The scientists report in the Proceedings of the Royal Society B that the hybrid has taken over all but one of the 10 seagrass meadows surveyed. The clone is 1.5 orders of magnitude larger than the largest fungi and longest sea animal.

The clone has been spreading since 4500 years ago, according to the team. It would make it among the oldest organisms on Earth, but not as old as the oldest tree.

Global warming is making it harder for the plants to hang on to their roots at the northern edge of Shark Bay. The water has become much saltier because of low rainfall and high evaporation rates. The authors note that the clone's extra genes may be able to adapt to these stresses.