Study suggests Wrangel’s last woolly mammoth survived thousands of years despite inbreeding Ecology | magazine

The last woolly mammoth population was isolated 10,000 years ago on Wrangel Island, off the coast of Siberia, when sea levels rose and separated the mountainous island from the mainland.

A new genomic analysis reveals that the isolated mammoths, which lived on the island for the next 6,000 years, originated from a maximum of 8 individuals, but grew to 200-300 individuals over 20 generations. European press.

Researchers report in the magazine cell The genomes of the Wrangel Island mammoths showed signs of inbreeding and low genetic diversity, But not to the point of being able to explain its eventual (and mysterious) extinction.

“We can now confidently reject the idea that the population was simply too small and was genetically doomed to extinction,” says lead author Love Dalén, an evolutionary geneticist at the Centre for Palaeogenetics, a collaboration between the Swedish Museum of Natural History and Stockholm University. “This means that it was probably just a random event that killed them off, and if that random event had not happened, we would still have mammoths today.”

In addition to shedding light on woolly mammoth population dynamics, this analysis of Wrangel Island mammoths could help guide conservation strategies for currently endangered animals.

“Mammoths are an excellent system for understanding the current biodiversity crisis. “What happens from a genetic point of view when a species passes through a population bottleneck, because it mirrors the fate of many current populations,” says first author Marianne Dehascq of the Centre for Paleogenomics.

To understand the genetic consequences of the Wrangel Island bottleneck on mammoth populations, the team analyzed the genomes of 21 woolly mammoths: 14 from Wrangel Island and 7 from pre-bottleneck mainland populations. In total, the samples spanned the last 50,000 years of woolly mammoth existence, providing a window into how mammoth genetic diversity has changed over time.

Compared with their continental ancestors, the genomes of mammoths on Wrangel Island showed signs of inbreeding and decreased genetic diversity. In addition to decreased overall genetic diversity, they showed decreased diversity in the major histocompatibility complexa group of genes known to play a critical role in the vertebrate immune response.

The researchers showed that the genetic diversity of the population continued to decline throughout the 6,000 years that mammoths inhabited Wrangel Island, although at a very slow rate, suggesting that the population size remained stable until the end. Although the island’s huge population has gradually accumulated rather harmful mutations over the course of its 6,000 years of existence,The researchers showed that the population was slowly getting rid of the most harmful mutations.

He points out, “If an individual has a very harmful mutation, they are basically not viable, so those mutations gradually disappeared from the population over time, but on the other hand, we see that mammoths accumulated slightly harmful mutations until they almost became extinct.” Outside. “It is important that current conservation programs take into account that it is not enough to restore populations to a decent size.; It should also be actively monitored genetically because these genomic effects can persist for more than 6,000 years.

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Although the mammoth genomes analyzed in this study span a long period of time, they do not include the last 300 years of the species’ existence. However, researchers have discovered fossils from the late mammoth period and plan to conduct genetic sequencing in the future.

“What happened in the end remains a mystery.“We don’t know why they became extinct after being in fairly good shape for 6,000 years, but we think it was something surprising,” Dallin emphasizes. “I would say there is still hope of finding out why they became extinct, but there are no promises.” (Yo)