New research has revealed that the Norwegian lemming is one of the youngest mammals on Earth. The team found that the Norwegian lemming split from its closest relative, the Western Siberian lemming, about 35,000 years ago. Although this may seem like a long time ago, from an evolutionary perspective, it might as well have been yesterday.
Scientists used advanced whole-genome sequencing to uncover the lemming’s surprising evolutionary history, with the results published in the Proceedings of the National Academy of Sciences. This recent split occurred during the climax of the last Ice Age, making the Norwegian lemming an incredibly unique evolutionary case.
“The Norwegian lemming is a key ecological species in the Fennoscandian tundra. Among other things, it serves as primary food for many predator species, including some threatened ones such as the Arctic fox,” said David Díez del Molino, a researcher at the Centre for Palaeogenetics and the Department of Zoology at Stockholm University, in a press release. “However, it is also a very interesting species from an evolutionary perspective, which so far has not been studied using genomics. Our study starts to fill that gap.”
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One of the Youngest Mammals on Earth
Jaw from an ancient lemming. (Image Credit: Vendela K. Lagerholm)
To understand how the lemming species evolved, researchers looked at the genomes of nine living lemmings and two ancient ancestors. The data they analyzed confirmed that Norwegian and Western Siberian lemmings each belong to their own distinct evolutionary branch.
One of the most interesting data points to come out of the research of these two branches was that there was no evidence of interbreeding, which is rare for species that have recently split and that occupy the same geographic regions.
“Our findings indicate that the Norwegian lemming is among the most recently evolved mammals, diverging from its sister taxon, the Western Siberian lemming, at a remarkably shallow time depth. After this, these species seem to have remained isolated, as we don’t find any indication of interbreeding between them,” said Edana Lord, postdoctoral researcher at Stockholm University, in the press release.
The lack of interbreeding is unexpected, as species of mammals that split apart often still share some genetic material. However, these two lemming populations appear to have stayed genetically separate.
DNA Clues To Fur, Fat, and Survival
A Norwegian lemming peeks out from under rocks in Sarek National Park, Sweden. (Image Credit: Love Dalén)
Researchers also discovered hundreds of mutations found only in the Norwegian lemming. These mutations were mainly in genes linked to fur color, fat storage, and even behavior. These evolved traits may help explain how the Norwegian lemming survives harsh climates.
The Norwegian lemming has a striking coat of black-and-yellow fur that scientists have often associated with its ability to successfully thrive in its Fennoscandian environment. Additionally, this species of lemming is incredibly active, even during the winter months, which also helps them survive and avoid predators.
Another thing the study has helped clarify is how different lemming species are related. Beyond showing the split between Norwegian and Western Siberian lemmings, the team was also able to identify a third taxonomic group: the Eastern Siberian lemming, or Lemmus paulus.
In the future, researchers hope to continue to use modern genetic tools to help explore these three groups of lemmings and to learn more about the connections between the environment and these exciting, rapid evolutionary splits.
“This work represents a big step in our understanding of lemming speciation and evolution. It paves the way for exciting future research, particularly in exploring ancient gene flow and precisely dating the emergence of the unique genetic adaptations we see in the Norwegian lemming,” said Love Dalén, professor in Evolutionary Genetics at Stockholm University, in the press release.
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