A study conducted by researchers from Brazil, Argentina and the United States suggests that the Cerrado may have been, in the last million years, a center for the emergence of new species of leafhopper, as the ants of the genus are known. Atta. However, the recent expansion of agriculture in the region seems to be negatively affecting the biodiversity of these insects in the region – precisely favoring species considered pests for agriculture.
Published in the journal Systematic Entomology, the work indicates that the origin of the saúvas took place around 8.5 million years ago somewhere in the so-called Mesoamerica, a region that currently ranges from southern Mexico to northwestern Colombia. Subsequently, these insects would have spread across South America, mainly from the cerrado. Also according to the study, an explosion of new species may have occurred between one and three million years ago, just when the Cerrado was expanding.
“The expansion of the Brazilian Cerrado apparently favored the saúvas, as it provided greater food diversity and more open environments, to which they adapted very well. The saúvas became specialized in these different habitats and generated new species”, explains Corina Barrera, first author. of the study, carried out during his doctorate at the Institute of Biosciences of the Universidade Estadual Paulista (IB-Unesp), in Rio Claro.
“If the cerrado ends, they may experience a new retraction in terms of biodiversity, like others that occurred in the past. This may already be happening with the introduction of extensive agriculture in the region. We have not yet measured the magnitude of this phenomenon. that there is a large population explosion of saúvas, but with low biological diversity, caused by the expansion of agriculture. The few species that benefit from crops such as soybeans and sugarcane, for example, become pests. forests, which do not adapt to crops, can suffer a great extinction”, says Maurício Bacci Júnior, professor at IB-Unesp and coordinator of the study.
The work integrates two projects supported (19/24470-2 and 19/03746-0) by Fapesp and coordinated by Bacci, one of them within the scope of a partnership between the National Science Foundation, of the United States, and the Biota-Fapesp Program.
To carry out the work, the researchers collected samples from 865 colonies of saúvas, in 19 countries and in 25 of the 26 Brazilian states. 224 specimens were selected for DNA extraction, from which 2,340 of the so-called ultraconserved elements were recovered, regions of the genetic code identical in more than one organism. Comparison of these elements is a tool known to determine evolutionary relationships quite accurately.
farmer ants
Although from the human point of view the saúva is considered an agricultural pest, these insects have practiced agriculture since before the emergence of man on Earth.
While most ants are hunter-gatherers, killing prey or eating what they find along the way, ants are part of a subtribe, called Attina, which between 50 million and 60 million years ago started to produce its own food.
“The inventors of agriculture are the ants and some groups of termites and beetles. They are insects that began to feed on fungi and evolved to cultivate them inside their nests, on top of some substrate. In the case of leaf-cutting ants, leaves and other plant remains. As a result, they have a food source that lasts all year round and achieve a certain food security”, defines Bacci, who is linked to the IB-Unesp’s Center for the Study of Social Insects (Ceis).
So long practicing agriculture made it possible for ants to even produce their own pesticides. In the case of a group older than the saúvas, for example, this occurs through a relationship of mutualism with bacteria. Microorganisms protect the fungi that feed the ants against pathogens. Recently, compounds used by one of these bacteria have been explored as possible drugs for human diseases.
But while these older ants use plant remains, such as flowers and leaves fallen to the ground, as a substrate to cultivate fungi, the so-called leaf-cutting ants, of which saúvas (genus Atta) and quenquém (genres acromyrmex and amoimyrmex), actively cut leaves to take to the nests. Hence they become potential pests.
Emerged around 19 million years ago, having divided into the two most recent genera (Atta and acromyrmex) around 16.5 million years ago, leaf-cutting ants are the most recent among fungus-growing ants. When it comes to saúvas, some species are even younger, having appeared between 1 million and 300 thousand years ago, such as the black saúva (Atta robust), in the latter case.
It barely appeared on Earth and is already threatened with extinction. Restricted to coastal regions of Rio de Janeiro and Espírito Santo, the black anteater is considered “vulnerable” by the Red Book of Brazilian Fauna Threatened with Extinction. One of the explanations for the threat is its low capacity to adapt to other habitats.
Other species, however, have their area enlarged as man increases his domain and, therefore, they are in frank expansion. One of them is the lemon anteater (Atta sexdens), which gets its name from the characteristic smell it gives off when its head is crushed, but is more famous for decimating entire crops, sometimes overnight.
“A plantation of anything that is not native to South America, as are the main agricultural crops, will always also be a ‘plantation’ of ants”, says Bacci.
The researcher is currently mapping the genes present in saúvas, in order to find characteristics (genetic signatures) that may have made them successful or on the way to extinction. In addition to better understanding the natural selection that took place in the group, the work may pave the way for the development of more targeted ant killers, which target only the genes of these harmful and expanding species, and not those of other harmless ants, in addition to fish, birds and mammals.
