The genomic secrets of how the muskox survived until today
At the end of the last Ice Age, many iconic species became extinct. However, one Ice Age relict, perfectly adapted to the harsh climate of the tundra environment, has survived until the present day. In a new research study in Molecular Ecology, scientists investigate how the muskox mastered living on the edge – geographically, ecologically, and genetically.
The muskox lives at the northern edge of the world, with native populations currently found in Canada and Greenland. To explore the eventful evolutionary history that brought the muskox here, a research team analyzed whole genomes of more than 100 muskoxen.
Through challenging field work in the High Arctic and collaboration with local communities and organizations, the team has secured samples from the most remote places in Canada and Greenland, and even one ancient muskox sample from Wrangel Island in Siberia, which was dated to ~21,000 years ago.
“Despite the wealth of genomic data that we were working with, reconstructing the muskox’ past was an arduous task because life in the Arctic is complicated. A lot of the signals that we were getting from our analyses seemed contradictory,” says Dr. Patrícia Pečnerová, who is a postdoc at the University of Copenhagen and Copenhagen Zoo in Denmark, and the first author of the study.
Dr. Patrícia Pečnerová did her PhD on woolly mammoth genomics at the Department of Zoology at Stockholm University and was co-affiliated to the Swedish Museum of Natural History.
What is clear from the results is that the muskox lost a big proportion of its genetic diversity in the last 20,000 years.
“By using an ancient Siberian genome, we were able to put the low diversity of present-day muskox into the context of their evolutionary history,” explains Dr. Edana Lord, postdoc at the Centre for Palaeogenetics, a joint venture between Stockholm University and the Swedish Museum of Natural History. She led the analyses of the ancient muskox.
Even the most diverse present-day muskoxen have only about a third of the diversity that the Siberian muskox had 20,000 years ago. In East Greenland, where the muskox arrived last on its long colonization journey, the level of genetic diversity is so low that there are only 2 variable positions for 100,000 base pairs.
Today’s Scandinavian muskox were extremely inbred
“This suggests that today’s Scandinavian muskox were extremely inbred even before they were reintroduced in the 1940s, this because they originated from the population in eastern Greenland which we can show in this article is highly inbred. It would actually be very exciting to investigate how much the inbreeding in Sweden has increased since then”, says Love Dalén, professor of evolutionary genomics at the Centre for Palaeogenetics, and co-author of the study.
While most animals with similar low levels of genetic diversity are iconic endangered species, the muskox is a geographically widespread species that counts about 170,000 animals. So how do muskoxen thrive almost without genetic diversity?
Reconstructing changes in population size through time, the researchers observed that the muskox started to decline already about 30,000 years ago, which is a time period that coincides with the maximum extent of the ice sheets covering Canada and Greenland. The slow and continued decline might have provided enough time for the most deleterious variation to be removed from the muskox’ gene pool.
More information
The study was an international effort that involved 31 co-authors led by researchers at the University of Copenhagen, and was supported by the Independent Research Fund Denmark, the Carlsberg Foundation, Bolin Centre for Climate Research, the Swedish Polar Research Secretariat and other partners.
The article “Population genomics of the muskox' resilience in the near absence of genetic variation” is published in Molecular Ecology.
Last updated: November 24, 2023
Source: Communications Office