Ancient DNA supports southern survival of R ichardson's collared lemming ( D icrostonyx richardsoni ) during the last glacial maximum

Abstract

Collared lemmings (genus D icrostonyx ) are circumpolar A rctic arvicoline rodents associated with tundra. However, during the last glacial maximum ( LGM ), D icrostonyx lived along the southern ice margin of the L aurentide ice sheet in communities comprising both temperate and boreal species. To better understand these communities and the fate of these southern individuals, we compare mitochondrial cytochrome b sequence data from three LGM ‐age D icrostonyx fossils from south of the L aurentide ice sheet to sequences from modern Dicrostonyx sampled from across their present‐day range. We test whether the D icrostonyx populations from LGM ‐age continental USA became extinct at the P leistocene– H olocene transition ~11000 years ago or, alternatively, if they belong to an extant species whose habitat preferences can be used to infer the palaeoclimate along the glacial margin. Our results indicate that LGM ‐age D icrostonyx from I owa and S outh D akota belong to D icrostonyx richardsoni , which currently lives in a temperate tundra environment west of Hudson Bay, Canada. This suggests a palaeoclimate south of the Laurentide ice sheet that contains elements similar to the more temperate shrub tundra characteristic of extant D . richardsoni habitat, rather than the very cold, dry tundra of the N orthern A rctic. While more data are required to determine whether or not the LGM southern population is ancestral to extant D . richardsoni , it seems most probable that the species survived the LGM in a southern refugium.

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