Biogeographic history of the Late Pleistocene and Holocene European small hamsters (subfamily Cricetinae).

The prevailing paleobiogeographic hypothesis suggests that many steppe and tundra-steppe taxa currently found in Central Asia expanded into Europe during Pleistocene glacial periods, when open habitats dominated. However, previous studies have shown that one such species, the European narrow-headed vole (Stenocranius anglicus), diverged from its Asiatic counterparts over 200 thousand years ago, implying its prolonged isolation and survival in European refugia through the Eemian interglacial period. To test whether this was an exception or part of a broader pattern, we analysed the mitochondrial genomes from 33 Late Pleistocene and Holocene small hamster (Cricetinae) remains from Central and Western Europe, the Balkans, and Anatolia, all previously identified morphologically as grey dwarf hamster (Nothocricetulus migratorius). Contrary to expectations, 16 Late Pleistocene Central European samples were assigned to the hairy-footed hamster (Cricetiscus sungorus), a species currently restricted to northern Kazakhstan and southern Russia, whereas 17 samples from the Balkans and Anatolia belonged to the grey dwarf hamster. In both cases, the Late Pleistocene samples formed clades sister to modern populations; however, with relatively recent divergence times. This suggests population continuity or repeated expansion of hamsters from Asiatic sources rather than long-term isolation in Europe, as previously observed in narrow-headed voles. Our findings indicate that steppe species, despite occupying similar ecological niches, respond to past climate change in a species-specific manner. Therefore, broad generalisations regarding their evolutionary history may be misleading.