Late Pleistocene to Recent Survival of True Lemmings (Lemmus, Cricetidae) Across the Palearctic Revealed by Modern and Ancient Mitogenomes

The analysis of mitochondrial genomes from an expanded sample of Lemmus across its Palearctic range, including Late Pleistocene specimens from eastern regions representing multiple time points, refines our understanding of the genus’ evolutionary history in the context of climatic oscillations over the last 50,000 years. Contrary to previous studies but consistent with paleogeographic expectations, we detected significantly higher genetic diversity in non-glaciated areas than in formerly glaciated regions. Our results do not support synchronous repeated turnovers across Western Eurasia during the Late Pleistocene. Instead, haplotypes shared among sites persisted across multiple temporal intervals. The data support post-LGM colonization of Scandinavia and the Kola Peninsula, most likely during the Late Dryas. Temporal analysis of mitochondrial haplotypes indicates the combined effects of genetic drift and bottlenecks, consistent with the extremely low haplotype and nucleotide diversity observed in contemporary Norwegian lemming populations. In contrast, high genetic diversity in eastern Siberian populations suggests long-term demographic stability and prolonged persistence. Pre-LGM and LGM specimens cluster with their respective geographic clades among modern samples, further supporting this interpretation. The well preserved Yakutian mummy, the oldest studied specimen dated forty thousand years ago, possessed highly divergent haplotype and its basal phylogenetic placement, considered alongside the antiquity of the specimen, could be consistent with the retention of ancestral polymorphism predating the major split in Eurasian lemmings or may represent a previously unrecognized and now extinct lineage. Distinguishing between these scenarios will require genome-wide nuclear data and expanded sampling of temporally stratified ancient material.