An explosion in snake diversity has come after a major moment in Earth’s history

When dinosaurs died out, they left big shoes to fill just about every ecosystem on our planet. Even without feet, the snakes rose to the challenge.

Shortly after the asteroid impact, some 66 million years ago, new models suggest that several undulating survivors quickly crept into unchallenged space. The dominance of the dinosaurs had ended, and it was time for birds, mammals and legless reptiles to explode.

“The diversification of mammals was so impressive that the Cenozoic is commonly referred to as the ‘age of mammals'”, the researchers write in a new article on the subject.

“With almost as many species of snakes as there are mammals, the Cenozoic might just as well be called the ‘age of snakes.’

Today there are nearly 4,000 different species of snakes. Where does this enormous diversity come from, when and why are questions scientists are still trying to understand.

Snakes are very rare in the fossil record, and those alive today are shy and secretive, making data collection difficult. Historically, these creatures have also been overlooked by scientists in favor of warm-blooded organisms more similar to us.

Unfortunately, the simple lack of information means that our models of snake evolution contain a lot of uncertainties.

The new model tries to take into account as much as possible the gaps in our knowledge. He compares published data on 882 living snake species to stomach contents of preserved museum specimens.

This is the first time that stomach data has been incorporated into evolutionary snake analysis, and although there is still a long way to go (the data includes less than a quarter of all snake species described), the results suggest that animal lines will rapidly diverge if given the ecological desirability.

The result is a burst or “explosion” of diversity, which then gradually slows down as a niche in the ecosystem becomes saturated.

According to the new model, ancestral snakes appear to have been narrowly specialized in what they could and could not eat even before the extinction of the dinosaurs. In fact, the most recent common ancestor of all snakes living today most likely fed on invertebrates, such as insects.

It was only after the asteroid impact killed most of the non-avian dinosaurs that the snakes began to branch out and try new flavors. The new model suggests that most snakes alive today originate from a lizard-eating ancestor in a relatively short period of time, although the exact timing will continue to be hotly contested.

While new research predicts that snakes exploded in diversity right after the dinosaurs went extinct, other models suggest that this happened millions of years later, during a smaller extinction event in the Eocene.

“The point is, in any case – their tree or our tree – the vast majority of snake diversification occurs after the asteroid impact,” evolutionary biologist Nick Longrich, who wrote his own models not so long ago. .

“Does this happen immediately after the asteroid (as they suggest) or does it only happen millions of years later, after this second extinction? Their diversity is fairly recent anyway. , but how many species survived, what groups radiated when… we’re probably going to be working on this for years to come. “

Snakes, it seems, have a peculiar way of twisting and turning to accommodate just about any ecological position.

Overall, they manage to eat a wide variety of diets, although some species have come to specialize to the extreme. For example, some snakes today need a specific venom for the type of prey they are hunting, while others need unique teeth and jaws to swallow their victims.

Whether this diversity of diet exploded soon after the extinction of the dinosaurs or millions of years later, it appears that ancient snakes had the ability to alter their predatory behaviors with remarkable flexibility.

In the Eocene, for example, when small mammals were taking flight, new models suggest that the more recent ancestors of vipers, boas, and pythons were already highly specialized in eating rodents. Whether this is the oldest example of rodent consumption among snakes, however, is limited by our selection of fossils.

“We are seeing a major explosion in snake diet diversification after the dinosaurs have gone extinct, and we are also seeing that when snakes arrive in new places, they often experience similar explosions of dietary diversification,” he said. he adds. Explain evolutionary ecologist Michael Grundler of the University of California at Los Angeles.

Colubroids, for example, are the largest family of snakes today, including the boomslang, whipsnakes, and the tree-dwelling brown snake, and are found on all continents except Antarctica.

Following the initial explosion of this family in the early Cenozoic, the new model suggests that its members continued to colonize North and South America, causing further spurts of adaptive evolution.

A population of colubroids in the Galapagos, for example, discovered how to hunt fish along the coast, which is a highly specialized behavior not seen in other close relatives.

Perhaps it was the adoption of special hunting behaviors like this that ultimately led to the evolution of niche diets in the snake lineage.

This is interesting, because it is often assumed that dietary generalists are much better at dealing with changing ecological conditions, while specialists are more limited in what they can and cannot do to survive.

“It is clear that specialization is not at a disadvantage,” Grundler told ScienceAlert.

“And one insight to take from analyzing all of these first-hand observations about the diet is that even apparent specialists occasionally diversify. Perhaps these rare sources of ecological variation are what keep snakes going on. innovate in the long term. “

The study was published in PLOS Biology.

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