New York —

We usually think of evolution as a process that inevitably runs forward. A species of giant-headed ants, however, seems to give clues that the dynamics may be much more complex, with transformations that make them return to forms of the past.

Photo:
Rockefeller university

When we talk about evolution we imagine an advance, a change with which a species becomes more specialized and complex in order to survive.

But is it possible that this species, instead of becoming increasingly sophisticated, begins to return towards forms and functions that you had left behind millions of years ago?

That involutionary process is what seems to happen with turtle ants, specifically with those who have the task of being soldiers within that species.

The soldier caste of turtle ants have overly large heads they use as shields to block the entrance to the tunnels in the branches of the trees they inhabit.

But these soldiers have reached such a level of sophistication that not all their heads have the same appearance.

Some have it in the form of a plate, like a manhole cover that perfectly seals the entrance to the tunnels.

That of others is more square, and they use it as blocks that are assembled with the heads of other ants to block the hole where some can enter threat.

Those differences in the design of their “shields” are a sample of how evolution works, but a new study reveals that in the case of these ants, history is more complicated.

Rockefeller University Soldier turtle ants have different ways to block their tunnels, depending on the shape of their heads.

“You would think that once a species specializes, it is trapped in a very narrow niche,” says Daniel Kronauer, head of the Laboratory for Evolution and Social Behavior at Rockefeller University (United States) and co-author of the research.

“But turtle ants are an interesting case of a very dynamic evolutionary trajectory.”

Private soldiers and elite troops

Turtle ants they don’t dig their own tunnelsThey take possession of those that have been punctured by other insects, such as beetles.

Since they cannot control the size of the ducts, what they did was evolve the size and shape of their heads so that they will adjust to the entrance hole of these cavities.

“The relationship between the heads of the turtle ants and the tunnels can offer a unique and clear vision of the natural selection“Write the authors of the research.

To better understand the evolution of these insects, the researchers analyzed the genetic information of 89 species of turtle ants, grouped according to the shape of the head of their soldiers, either square or disk-shaped.

.: The case of turtle ants show that evolution may be a more complex process than we think.

In addition, they included a species of turtle ants that it has no soldiers.

If evolution were to move in one direction, the researchers argue, the first turtle ants that appeared 45 million years ago would have no soldiers, and then would have gradually evolved, first creating “private” soldiers with square heads until reaching the most specialized ones, with disk-shaped heads that seem to be tailored to the tunnel holes.

Genetic analysis, however, revealed a different process. The oldest common ancestor that the researchers were able to trace most likely had a square head.

This evolved into a variety of species, from ones that did not have soldiers to others that included various levels of specialization.

Following the path of lineages, scientists even noted that in some cases, more specialized species had reversed course, engaging heads with more generic forms.

.The turtle ants seek to diversify their adaptation strategies.

According to experts, this mix of generic and specialized forms may be related to a form of diversification of the adaptation strategies of the species.

Flexible evolution

This finding shows “what surprisingly flexible what nature can be by adapting the shape of an organism to the context of the environment they inhabit, ”says Scott Powell, a biologist at George Washington University and co-author of the study.

According to Powell and his colleagues, these soldier turtle ants are a case of evolution. “reversible”.

“This redefines what we knew about the caste evolution“Concludes the study.

“These findings reject a process stable and directional in favor of a dynamic process of adaptive adjustments between the phenotype (the physical characteristics) and the environment ”.

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