In the Devil's Garden
One thing is often clear in people's ornamental green environment: when the dandelion boldly sticks its head out of the English lawn, it's obvious that a chemical mace will be used. Ants are sometimes similar to us, because some of them are also passionate about gardening - including the use of poison. In the rainforest of the Amazon Basin, a variety of species proliferates, which produces myriads of unusual creatures such as the candiru fish, which sometimes parasitically penetrates the urethra of bathers, soup plate-sized spiders, pink river dolphins, blood-sucking bats or the red uakari, a bald-headed monkey. With all these strange creatures, it is no wonder that the people of this wilderness have developed a large number of myths, legends and fairy tales related to the animals and plants of their homeland.
So, according to the Shuar people, the anaconda will one day bring the end of the world with a flood. And according to the stories of the Cario Indians, the Mapinguari wanders through the depths of the jungle at night - a kind of giant sloth that is said to spread a truly bestial smell and even kills inexperienced hunters. Perhaps there is actually a grain of truth behind one or the other legend, an unknown animal behavior or a new species. But in the absence of scientific knowledge, in these cases stories explain and interpret the secrets of the forest.
For the Matses Indians in the Amazon basin of Peru, the so-called "Diablo Chacra", the devil's gardens, are as nebulous as the nocturnal screams and the secret life of the mysterious Mapinguari for the Cario: diving in the middle of one of the most species-rich ecosystems on earth suddenly sparse and monotonous patches of vegetation in which only one tree species dominates – the blushing plant Duroia hirsuta. Who else but an evil spirit could be responsible for this when life is brimming with abundance all around?
The guardians have probably contributed to the eerie reputation of these monotonous stands and their "hellish" ambience, because the trees are vigorously defended by millions of ants of the species Myrmelachista schumanni, who live symbiotically in specially designed cavities of the Plant dwelling: Eating enemies who want to feast on the foliage of the plants are quickly put to an end. But what keeps these Duroia stocks so pure anyway? Does the plant keep the competition at bay by using toxins – a process that science calls allelopathy? Or are the ants, the busy gardeners, to blame?
Both are theoretically possible, which is why biologists led by Megan Frederick from Stanford University tested the corresponding behavior of the crawling animals on site in the Peruvian jungle. For several years, the researchers planted two saplings of the West Indian cedar tree (Cedrela odorata) each year in various devil gardens of different sizes. One was shielded from possible attack with a sticky insect repellent, while the other was exposed to the rigors of the harsh outdoors.
As soon as the eager guardians of the garden became aware of the supposed intruders, they began their attack. But what was in vain for the protected cedars due to the lack of an opportunity to attack ended fatally for their defenseless companions: within 24 hours, most of the leaves on the small tree died, and after five days it was almost completely defoliated - in complete contrast to the untreated control cedars in the Forest outside Devil's Gardens, although it's also crawling with predators.
However, the ants do not rely on mechanical defoliation through bites to protect their host plants, they take much more radical action against the sturgeon plants - with formic acid, as chemical analyzes revealed. When the insects inject this toxin into the unwanted leaves along their vascular pathways, it quickly reaches every branch of the plant, where it causes necrosis. Consequently, it is killed from within and eliminated as competition.
Now the scientists wanted to know whether this aggressive behavior of the insects against foreign plants is also triggered when they offer them cavities in the stem known as Dormatia, similar to Duroia hirsuta, as accommodation. But even adding artificial roosts to Cedrela odorata did not save the trees from dying. On the other hand, even specimens of the blush family from which the dormia had been removed were left alone by the kerfes. The animals seem to be very good at distinguishing between plant species, sparing those that bring them potential benefits.
With this diabolical behavior towards the plants, Myrmelachista schumanni secures an ecological niche with a safe home and sufficient living space for itself and above all for the numerous offspring. Frederick estimates that a single average colony can house up to 15,000 queens and three million workers. With the use of their own herbicide, they are constantly expanding their kingdom and possibly preserving it over the centuries. The largest devil's garden investigated could well have existed for 800 years - in the fast-paced rainforest, a legendary age, not only in the eyes of the Indians.