Environmental changes prompt species to adapt and evolve. This idea is one of the most established pillars of the theory of evolution, and there are thousands of examples in nature that confirm it. But can the reverse process also happen? That is, in which cases is it the evolution of the species that drives the change in environment? A team of researchers from the University of Rhode Island in the United States believes so, and in an article published today in Proceedings of the National Academy of Sciences they provide the best evidence to date of this ‘reverse evolution’.
The case of the white moth in England during the Industrial Revolution is perhaps the most classic and well-known example of a species being forced to change in order to survive. As coal smoke darkened the bark of trees near booming industrial cities, the white-bodied pepper moths sitting on them became perfect targets for hunters, bright dots on a black background, causing their numbers to boom. decreased from Meanwhile, however, black-bodied moths, once very rare, thrived and became dominant in that suddenly dark environment.
Throughout the history of life, examples are numerous. Fish, without going further, turned their fins into legs when they left the sea about 400 million years ago to conquer the mainland, which was previously uninhabited. And it was also the case that much later, “only” 50 million years ago, some of them “repented” and decided to return to the sea, as is the case with the whale, which has five of its hind fingers under its fin. There are bones. Likewise, tree-dwelling dinosaurs were gradually converting their forelimbs to feathers, giving rise to birds, far more efficient in that environment.
We humans stood up, with our hands empty, mammals became gigantic when the dinosaurs disappeared, trees competed in height to win a spot in the sun… the present we live in, from a still picture of a constant Not much in the developed world. And over the years, scientists have wondered whether evolution can work ‘in the opposite direction’ as well. Looks like the new study shows that it is.
lizards and their feet
In their work, the researchers show that an evolutionary change in lizard leg length had a significant impact on the growth of vegetation and spider populations on a series of small islands in the Bahamas. The authors say this is the first time that such dramatic effects of reverse evolution have been documented in a natural setting.
Jason Kolbe, one of the paper’s lead authors, explains, “The idea here is that, in addition to the fact that the environment shapes an organism’s traits through evolution, the same physical changes feed back into the system and drive change.” Do. Creatures.” Predator-prey relationships and other ecological interactions between species. We really need to understand how these dynamics work in order to predict how populations will persist and what kinds of ecological changes might occur.”
20 years job
For the past 20 years, Kolbe and his colleagues have been observing the evolutionary dynamics of anole lizard populations on a series of small islands in the Bahamas. The chain is made up of about 40 islands, ranging from a few dozen to a few hundred meters across, which are small enough to keep a close eye on the lizards that live there. In addition, the islands are far enough apart that the lizards cannot easily move from one to another, so the different populations may be isolated from each other.
Previous research had already shown that the brown mole quickly adapted to the characteristics of the surrounding vegetation. In habitats where the diameter of brush and tree branches is small, natural selection favors lizards with shorter legs, allowing individuals to move faster when evading predators or chasing insects. In contrast, lankier lizards do better where tree and plant branches are thicker. The researchers have shown that this limb-length trait could have evolved rapidly in brown shrews in just a few generations.
In this new study, Kolbe and his team wanted to see how such a change in limb length might affect the island’s ecosystem. The idea was to isolate the short-legged and long-legged lizards on their own islands, and then observe how the lizard populations affected the ecology of their respective homes.
Because the islands in the experiments were mostly covered by small-diameter vegetation, the researchers expected that the more agile short-legged lizards would be better adapted to such an environment, able to capture more prey in the trees, and their There will be VD for a long time. – Foot companions. The question was whether the ecological effects of these highly effective predators would be detectable.
Separating short leg from long leg
The next step was to capture hundreds of brown moles to measure their leg length, keeping only those with especially long or short legs and returning the rest to their environment. With the two populations of lizards being well differentiated, all they had to do was release them on separate islands (and where there were no lizards before) and see what happened.
Eight months later, the scientists returned to those islands looking for possible ecological differences between them. And it turned out that not only were there, but the differences were considerable. On islands with short-legged lizards, populations of web spiders, a major prey item for brown anoles, were reduced by 41% compared to islands with long-legged lizards.
There were also significant differences in plant growth. Because the short-legged lizards were better at hunting herbivorous insects, the plants flourished. In fact, buttonwood trees on islands with short-legged lizards had twice as many shoots as trees on islands with long-legged lizards.
According to Kolbe, these results help to close the cycle of interactions between ecology and evolution: «These findings-he says- help us to close that feedback loop. We knew from previous research that ecological factors shape limb length, and now we show the correlation of that evolutionary change in environment.”
Fully understanding the extent of those interactions between evolution and ecology will help predict environmental consequences, the researchers say, especially as human activities accelerate the rate of evolutionary and ecological change around the world.
