70 years after the Gulag

Readers of “The Gulag Archipelago” by Aleksandr I. Solzhenitsyn (1974) might remember how the book starts: “In 1949 some friends and I came upon a noteworthy news item in Priroda (Nature), a magazine of the Academy of Sciences. It reported in tiny type that in the course of excavations on the Kolyma River a subterranean ice lens had been discovered which was actually a frozen stream – and in it were found frozen specimens of prehistoric fauna some tens of thousands of years old”. Indeed, in 1946 unnamed GULAG prisoners discovered a nest with three mummified carcasses of arctic ground squirrels in the permafrost sediments of the El’ga River, northeastern Siberia. They were attributed to a new species, Citellus (Urocitellus) glacialis because they differed in body morphology from arctic ground squirrels inhabiting this area at present.

Some 70 years later, Prof. Faerman (Faculty of Dental Medicine) and Dr. Kahila Bar-Gal (Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food & Environment) from The Hebrew University of Jerusalem, together with their Russian colleagues led by Dr. Formozov from the Lomonosov Moscow State University in order to verify the taxonomic status of U. glacialis and to explore the relationships of ancient and modern arctic ground squirrels launched a new study using comprehensive genetic and dating methods.

Today, arctic ground squirrels are found on both sides of the Bering Strait – northeastern Siberia in the west and northwestern North America in the east. There is a consensus in that for an accurate reconstruction of population history both modern and ancient DNA data are required. Prior to the current study the genetic make-up of ancient arctic ground squirrels was unknown and modern DNA data, largely limited to Alaska and northwestern Canada, have been used to reconstruct the genetic history of this species. Combining genetic findings with direct radiocarbon dating of fossils significantly improves our understanding of population dynamics over time. Dr. Boaretto from the Weizmann Institute of Science, who also participated in this study, dated the mummified remains to the Late Pleistocene period (ca. 30,000 years before present), nearly three times older than previously thought. Phylogenetic analyses performed in this study, based on complete cytochrome b gene sequences of five Late Pleistocene specimens from two permafrost sites and of modern arctic ground squirrels from 21 locations across northeastern Siberia, provided no support for earlier proposals that ancient arctic ground squirrels from Siberia constitute a distinct species. In fact, the researchers found direct descendants of the Glacialis family in the Kamchatka Peninsula and their close relatives in the Alaska Peninsula.

Altogether, the findings obtained in the study allowed the researchers not only to verify the taxonomy of U. glacialis and to explore the relationships between ancient and modern arctic ground squirrels in western Beringia but to view the entire process of diversification of arctic ground squirrels from a new perspective using a time-calibrated approach and to provide a precise timeline of these events. “This study highlights the importance of natural history collections for exploring modern and past biodiversity and reconstructing the phylogenetic history of species”, says Dr. Gila Kahila Bar-Gal, Head of the Laboratory of Molecular Evolution and Director of the National Natural History Collections of the Hebrew University.

Faerman, M. et al. DNA analysis of a 30,000-year-old Urocitellus glacialis from northeastern Siberia reveals phylogenetic relationships between ancient and present-day arctic ground squirrels. Sci. Rep. 7, 42639; doi: 10.1038/srep42639 (2017).