Myth, debunked: Fairy circles forming in Namibia are not caused by termites

The so-called “fairy circles” are naked, reddish circular spots It is found mainly in the grasslands of Namibia and northwestern Australia. Scientists have long debated whether these unusual patterns are caused by termites or to an ecological version of the self-regulating Turing mechanism. A few years ago, Stefan Getzen from the University of Göttingen found strong evidence to The last hypothesis in Australia. And now his team has found similar evidence in Namibia, according to new paper Published in the journal Perspectives in Plant Ecology, Evolution and Systematics.

“We can now reject the termite hypothesis permanently, because termites are not a prerequisite for the formation of new imaginary circles,” Getzen told Ars. This applies to both Australian and Namibian fictional circles.

as such inform us previously, Himba Bushmin In the Namibian grasslands, legends littered about the mysterious fairy-tale circuits of the region. It can reach several feet in diameter. They are called “footprints of the gods”, and are often said to be the work of the Himba deity MukuruOr an underground dragon whose poisonous breath kills anything that grows within those circles.

Scientists have their own ideas, and over the years, two different hypotheses have emerged about how circles form. One theory attributed the phenomenon to a special Types of termites (Custom Psammmmotermes), whose digging damages plant roots, causing excess rainwater to seep into sandy soil before plants can absorb it—giving termites a handy water trap as a resource. As a result, plants die again in a circle from the site of the insect’s nest. The circles expand in diameter during dry spells because termites must venture away from food.

The Another hypothesis-the one Adopted by Getzen– sees that circles are a kind of self-regulating spatial growth pattern (Turing pattern) that arises when plants compete for scarce water and soil nutrients. in 1952 seminal paper Alan Turing was trying to understand how natural, non-random patterns (such as zebra stripes) appear, and he focused on chemicals known as morphogens. He devised a mechanism that involves the interaction between an activating chemical and an inhibitory chemical that propagates throughout the system, much like gas atoms do in a closed box.

It is akin to injecting a drop of black ink into a beaker of water. Usually this leads to the stability of the system: the water gradually turns into a uniform gray color. But if the inhibitor spreads at a faster rate than the activator, the process is disrupted. This mechanism will produce a file Turing pattern: spots, stripes, or when applied to an ecosystem, Groups of ant nests or imaginary circles.

In 2019, Getzin . Team conducted a study From the fictional circuits of northwest Australia, near an old mining town called Newman. The team dug more than 150 holes in nearly 50 fairy circles in the area to collect and analyze soil samples, specifically to test the termite hypothesis. They also used drones to map larger areas of the continent to compare the gaps in vegetation usually caused by termites in the area, with the imaginary circles that sometimes form.

The vegetation gaps caused by the harvester termites were about half the size of the imaginary circles and much less arranged, so they didn’t find any tough subterranean plants that inhibited weed growth. But they found high soil compaction and clay content in the circles, and evidence of the contribution of heavy rain, intense heat and evaporation to their formation. “Termite constructions can occur in the region of fairy circles, but the partial local association between termites and fairy circles has no causal relationship,” Jetzen said at the time. “Therefore no destructive mechanisms, such as those found in termites, are necessary for the formation of distinct chimeric circle patterns; hydrological interactions between plant and soil are sufficient alone.”

Having effectively disproved the Australian termite origin hypothesis, Getzen turned his attention to testing the termite hypothesis specifically in Namibia, using a similar methodology. While his previous work on Namibian fictional circuits has not specifically addressed investigations of plant roots, this new study shows that plant roots are not affected by herbivores.

“For the first time, we went right after the rain to the fairy circles and checked the new grasses for herbivorous termites,” Getzen told Ars. “Our excavations show that termites certainly did not cause the grasses to die. If you were too late in the imaginary episodes, the weeds died long ago and perhaps destructive animals like termites may have already fed on the woody grass. But they didn’t kill the grass. We We show unequivocally that weeds die before and are completely independent of any termite action.”

So what’s next for Getzin? He believes that more research is needed on the intelligence of swarm plants, likening plants to beavers in the sense that they can act as “ecosystem engineers” who modify their environment. “Most people can’t believe this or aren’t willing to believe it, because plants don’t have brains,” Getzen said. “But plants behave similarly like beavers as ecosystem engineers because their only way to survive is to form strict geometric patterns” — in other words, Turing patterns.

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