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Genomic analysis reveals true origin of South America’s canids

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The main takeaway:

  • Dog puzzle. At the heart of ancient assumptions, researchers have found that a single dog-like species that entered South America less than 4 million years ago gave rise to all types of dogs today.
  • Rapid speciation. Within two million years, blink of an eye in evolution time, all ten extant species and some now extinct species evolved from that original group.
  • How did this happen? The research shows how quickly new species can emerge and spread geographically in environments where there is little competition.

South America has more dog breeds than anywhere on earth, and they’re surprisingly new Genomic analysis led by UCLA It shows that all these dog-like animals evolved from a single species that entered the continent only 3.5 million to 4 million years ago. Scientists have long assumed that these diverse species originated from multiple ancestors.

More surprising? The longest and shortest species are the most closely related.

Some of the key genetic mutations that led to the rapid emergence of extreme differences in height, size and diet of South American canines were artificially introduced through selective breeding over a period of a few thousand years to produce the amazing diversity seen in the most famous dogs. : domestic dog.

The research, published in the Proceedings of the National Academy of Sciences, shows how quickly new carnivore species can evolve and spread in environments lacking competition and provides guidelines for the conservation of threatened and endangered South American dogs.

Ten species within the family of dogs and wolves, known as canines, live in South America today. Seven foxes and three more exotic: the short-eared dog, the bush dog, and the wolf-wolf.

For years, scientists have had a theory about how South America became home to so many types of dogs. The continent had very few placental mammals, and no canine ancestors, until the volcanic strip of land known as the Isthmus of Panama rose above sea level about 3 million years ago, allowing free movement of animals between the continents. This is a short window for many species to evolve from a single ancestor, so scientists have hypothesized that multiple species of dogs entered through the isthmus at different times, giving rise to existing and now extinct species.

To find out how these species have long been related and by what genetic mechanisms they diverged, UCLA doctoral student Daniel Chavez, now a postdoctoral researcher at Arizona State University, and UCLA professor of evolutionary biology, Robert Wayne, sequenced 31 genomes. It includes everything found in South America. Kinds of dogs. They traced the evolutionary relationships between species by studying the locations, quantity, and types of genetic mutations between them.

Surprisingly, genetic data indicated a single ancestral group of dogs that reached between 3.5 million and 3.9 million years ago – before the isthmus rose fully – and includes about 11,600 individuals. These ancestors must have made their way south through the newly developed Panama Corridor, then just a narrow strip of savannah that was generally unnavigable by large populations, the researchers said.

“We found that all the dog species in the world came from a single invasion that entered South America east of the Andes,” Chavez said. “A million years ago, there were already a lot of dog species, but they weren’t very genetically distinct due to gene flow, which happens when groups can interbreed easily.”

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This species quickly spread throughout South America, including the thin strip of land west of the Andes, adapting to different environments and becoming more genetically distinct. The researchers found that the ten species that exist today all appeared between one and three million years ago.

They also discovered that the wolf-legged, the longest and tallest dog in South America and the only one that eats mostly fruit, and the shortest, the bush dog, which depends more on meat than wolves and African wild dogs, is the most closely related. Changes in the gene that regulates leg length are responsible for the height difference.

Five dogs appeared in a bush crossing a stream

Diego Torres/Napo Wildlife Center Ecolodge

A herd of bush dogs crossing a stream.

“There have also been many other now-extinct species of hypercarnivores associated with the bush dog,” Chavez said. “Maybe they were bigger in size, so to compete, the ancestors of the bush dog got smaller while the wolf with cubs got taller and eventually stopped competing for meat.”

This rapid and extreme speciation by natural selection is similar to the broad differentiation of domestic dogs, which occurred rapidly through artificial selection by humans.

“South American dogs are the domestic dog of the wild animal kingdom in that they vary greatly in leg length and diet, and these changes have occurred very quickly, within one to two million years,” Wayne said. “It’s a natural resemblance to what we did to dogs. It all happened because South America was free of this type of carnivore. There was a lot of prey and there were no large or medium-sized carnivores to compete with. In this empty place, nature allowed such This rapid radiation.”

The findings also highlight relationships between species and specific genes that can aid efforts to save species threatened by habitat loss and climate change.

“Darwin’s fox, which currently only lives on one island off the coast of Chile and very small areas on the mainland, is a good example of the need for conservation,” Wayne said. “We have demonstrated at the genome level that there are large differences in variance between species, with very low levels of variance and potentially harmful genes in the most endangered species. We can save small populations with studied captive breeding programmes.”

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