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The mammoth population on Wrangel Island remained stable before extinction

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Mammoth (Mammutus primigenius) is isolated Wrangel Island Mammoths were discovered off the coast of Siberia approximately 10,000 years ago and survived for over 200 generations before going extinct approximately 4,000 years ago. To study the evolutionary events leading up to their extinction, scientists analyzed the genomes of 21 Siberian mammoths and found that mammoth populations recovered quickly from a severe bottleneck and remained demographically stable for the next 6,000 years.

Three mammoths (Mammutus primigenius) walks up a snow-covered hill with snow-capped mountains rising behind him above a dense green forest of fir trees. Image by Daniel Eskridge.

“We can confidently reject the idea that the population was so small that it was destined to go extinct for genetic reasons,” said Dr Love Dalen, an evolutionary geneticist at the National Academy of Sciences of Canada. Center for PaleogeneticsIt is a joint collaboration between the Swedish Museum of Natural History and Stockholm University.

“This means that it was probably just a chance event that caused the mammoths to go extinct, and if that chance event hadn't occurred, mammoths would still be around today.”

“In addition to shedding light on the population dynamics of woolly mammoths, analysis of the Wrangel Island mammoths could inform conservation strategies for this currently endangered animal.”

“The mammoth is an excellent system for understanding the ongoing biodiversity crisis and what happens from a genetic perspective when a species experiences a population bottleneck, because it reflects the fate of many modern populations,” said Dr Marianne DeHask, also from the Centre for Palaeogenetics.

To understand the genomic impact of the Wrangel Island bottleneck on mammoth populations, the researchers analyzed the genomes of 21 woolly mammoths, 14 from Wrangel Island and seven from the mainland population that existed before the bottleneck.

Overall, the samples span the woolly mammoth's existence over the past 50,000 years and provide insight into how the animal's genetic diversity has changed over time.

Compared to their mainland ancestors, the genomes of the Wrangel Island mammoths showed signs of inbreeding and low genetic diversity.

In addition to the overall low genetic diversity, Major histocompatibility complexA group of genes known to play important roles in the immune response of vertebrates.

The scientists showed that the genetic diversity of the population continued to decline, albeit at a very gradual rate, throughout the 6,000 years that the mammoths lived on Wrangel Island, suggesting that the population size remained stable until the end.

They also showed that the island's mammoth population gradually accumulated moderately deleterious mutations over its 6,000-year existence, but that the most deleterious mutations were slowly eliminated.

“If an individual had a highly deleterious mutation, they would basically not be able to survive, so over time those mutations would slowly disappear from the population. But we know that mammoths accumulated mildly deleterious mutations almost all the way up until their extinction,” Dr DeHask said.

“It's important to remember that current conservation programs will not be enough to simply re-establish populations to a reasonable size. They also need to be actively and genetically monitored, as these genomic effects could last for more than 6,000 years.”

The mammoth genomes analyzed in this study span a long period of time, but do not include the last 300 years of the species' existence.

However, the authors plan to excavate fossils from the final stages of the mammoth and analyze its genome sequence in the future.

“What happened to them at the end is still a mystery. We don't know why they went extinct after surviving fairly well for 6,000 years, but we think it was probably a sudden event,” Dr Dallen said.

“I think there's still hope we can figure out why they went extinct, but I can't make any promises.”

of Investigation result Published in the online journal this week cell.

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Marianne DeHask othersTemporal dynamics of genomic erosion in pre-extinction mammoths. cellPublished online June 27, 2024, doi: 10.1016/j.cell.2024.05.033

Source: www.sci.news

Study finds that butterfly and moth genomes have remained remarkably stable over 250 million years of evolution

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This stability exists despite the incredible diversity in wing patterns, sizes, and caterpillar morphology across more than 160,000 species worldwide today, according to one study. new paper It was published in the magazine natural ecology and evolution.

lissandra belargas. Image credit: Eric Silvestre.

Butterflies and moths (in order) Lepidoptera) make up 10% of all described animal species and are extremely important pollinators and herbivores in many ecosystems.

In a new study, Professor Mark Blaxter and colleagues from the Wellcome Sanger Institute set out to understand the processes driving the evolution of chromosomes in this highly diverse group.

They analyzed and compared more than 200 high-quality chromosome-level genomes of butterflies and moths.

They identified 32 ancestral chromosomal components; Merian element Thanks to the work of pioneering 17th century entomologist Maria Sibylla Merian, most butterfly and moth species have remained intact since their last common ancestor more than 250 million years ago.

With the exception of a single ancient fusion event between two chromosomes that led to the 31 chromosomes found in most species today, the chromosomes of most modern species correspond directly to these ancestral Merian elements.

Researchers discovered that not only are chromosomes incredibly stable, but the order of genes within them is also stable.

They discovered several species with small changes, mainly involving the fusion of small autosomes and sex chromosomes. This highlights the role of chromosome length as a driver of evolutionary change.

However, scientists believe that the blue butterfly (lissandra) and the group containing cabbage butterflies (Pieris) ignored these genomic structure constraints.

These groups underwent large-scale chromosomal reshuffling, including large-scale chromosome reshuffling through chromosome breakage and fission and fusion.

This study improves our understanding of the factors that lead to genetic diversity in these insects. This will guide efforts to protect and conserve specific species facing unique challenges and environmental changes related to climate change.

“The chromosomes of most butterflies and moths living today can be directly traced back to 32 ancestral Merian elements that existed 250 million years ago,” said Dr. Charlotte Wright, researcher at the Wellcome Sanger Institute. said.

“It is surprising that even though the species has diversified extensively, its chromosomes have remained surprisingly intact.”

“This calls into question the idea that stable chromosomes may limit species diversification. Indeed, this feature may be the basis for building diversity. We We hope to find clues about rare groups that have circumvented these rules.”

“Studies like this that allow us to delve into these evolutionary processes are only possible through efforts like the Darwin Tree of Life Project, which generate high-quality, publicly available genome assemblies,” Blaxter said. the professor said.

“We are stepping up these efforts with Project Psyche, where we aim to sequence all 11,000 butterfly and moth species in Europe in collaboration with collaborators across the continent.”

“As important pollinators, herbivores, and food sources in a variety of ecosystems, and as powerful indicators of ecosystem health, a deeper understanding of the biology of butterflies and moths through Project Psyche will This will be useful for future research on adaptation and speciation for biodiversity conservation.”

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CJ light other. Comparative genomics reveals the dynamics of chromosome evolution in Lepidoptera. Nat Ecole Evol, published online on February 21, 2024. doi: 10.1038/s41559-024-02329-4

Source: www.sci.news