Novaya Zemlya
In 2021, a taxonomic study analyzing a distinct population of lemmings on Novaya Zemlya, previously thought to be Siberian brown lemmings ("Lemmus sibiricus"), found them to be more closely related to "L. lemmus", and reclassified them as a new subspecies "L. lemmus chernovi", or the Novaya Zemlya lemming, named after zoologist and academician of the Russian Academy of Sciences, Yury I. Chernov. It is currently only known from the southern island of the archipelago. It is thought that prior to the Eemian Interglacial, "L. lemmus" was distributed widely throughout the Arctic Shelf from Western Europe east to Novaya Zemlya, and sea level rise during the Eemian left the species in its present day disjunct distribution, with populations only on Fennoscandia and Novaya Zemlya. Novaya Zemlya may have served as a refugium for cold-adapted terrestrial fauna such as "L. lemmus" during the Pleistocene interglacial periods. The Novaya Zemlya lemming lacks the aposematic coloration of the Norway lemming, being dull in color and lacking antipredator adaptations. It is thought that the aposematic traits may be specific to the mainland population and evolved during its isolation in the Fennoscandian refugium.