Myth, busted: Namibia’s fairy circles are not caused by termites

So-called “fairy circles” are empty, with a reddish tint circular patch Found notably in the grasslands of Namibia and northwestern Australia. Scientists have long debated whether these unusual patterns are due to termites or an ecological version of a self-organizing Turing process. A few years ago, Stefan Getzin of the University of Göttingen found out illegible evidence for Next guess Australia. And now his team has found similar evidence in Namibia, according to a new paper Published in Perspectives in the Journal of Plant Ecology, Evolution and Systematics.

“We can now definitively reject the warming hypothesis, because termites are not a prerequisite for the formation of new fairy circles,” Getzin told Ars. This holds for both Australian and Namibian fairy circles.

as We have reported previously, Himba Bushmen Legend has passed about the region’s mysterious fairy circles in the grasslands of Namibia. They can be as large as several feet in diameter. Called the “Footprints of the Gods”, they are often said to be the work of Himba gods elderOr an underground dragon whose poisonous breath kills anything growing inside that circle.

Scientists have their own ideas, and over the years, two different hypotheses have emerged about how circles form. A theory attributed a particular phenomenon Species of whales (Psammotermes allocerus), whose ice damages plant roots, causing excess rainwater to seep into sandy soil before plants can absorb it—giving termites an easy water trap as a resource. As a result, plants die back in a circle from insect nests. During drought the circles expand in diameter because the termites must travel farther for food.

The Other assumptions– The only one Supported by GetZinCircles are one type Self-organized spatial growth patterns (a Turing pattern) in which plants compete for scarce water and soil nutrients. in him seminal 1952 paper, Alan Turing was trying to understand how natural, non-random patterns (like zebra stripes) emerge, and he turned to chemicals known as morphogens. He developed a method involving the interaction between an activator chemical and an inhibitor chemical that diffuses throughout a system, much as gas atoms would in an enclosed box.

It is like injecting a drop of black ink into a beaker of water. Usually this will stabilize a system: the water will gradually become a uniform grey. But if the inhibitor diffuses faster than the activator, the process is unstable. That process will produce a Turing pattern: spots, stripes, or, when applied to an environmental system, Cluster of ant nests or fairy circles.

In 2019, Getzin’s team conducted a study Fairy Circle in northwestern Australia near an old mining town called Newman. The team dug more than 150 holes in about 50 elk circles in the region to collect and analyze soil samples, specifically to test the termite hypothesis. They use drones to map large areas of the continent to compare vegetation gaps typically created by harvester termites in the region, sometimes with fairy circles.

Vegetation gaps created by harvester termites were about half the size of fairy circles and much less ordered, so they found no solid subterranean termiteria that would prevent grass growth. But they found high soil compaction and clay content in the circles, evidence of heavy rainfall, extreme heat and evaporation contributing to their formation. “Termite construction may occur in areas of fairy circles, but the partial local correlation between termites and fairy circles has no causal relationship.” At this time Dr. Getzin. “So no destructive process, such as from termites, is necessary to form distinct fairy circle patterns; only hydrodynamic plant-soil interactions are sufficient.”

After effectively disproving the Australian termite origin hypothesis, Getzin turned his attention to specifically testing the termite hypothesis for Namibia using a similar approach. Although his previous work in Namibian fairy circles did not specifically address the investigation of plant roots, this new study shows that plant roots are not touched by insects.

“For the first time, we went to the elm circle immediately after the rain and tested the new grasses for termite herbivory,” Getzin told Ars. “Our excavations show that the termites definitely did not cause the death of the grass. If you delay coming to the ellipse, the grass is long dead and detritivores like termites may have already fed on the lignified grass. But they didn’t kill them. The grass. We show unequivocally that the grass died earlier. goes and is completely independent of any thermal action.”

So what’s next for Getzin? He believes more research is needed on plant swarm intelligence, comparing plants to beavers in the sense that they can act as “ecosystem engineers” that change their environment. “Most people can’t believe it or don’t want to believe it, because plants don’t have brains,” says Getzin. “But plants act in the same way as beavers as ecosystem engineers because the only way they can survive is to create optimal, strictly geometric patterns”—in other words, Turing patterns.

DOI: Perspectives on Plant Ecology, Evolution and Systematics, 2022. 10.1016/j.ppees.2022.125698 (About DOI)