Glacial survival of the Norwegian lemming (Lemmus lemmus) in Scandinavia: inference from mitochondrial DNA variation

In order to evaluate the biogeographical hypothesis that the Norwegian lemm ing (Lemmus lemmus) survived the last glacial period in some Scandinavian r efugia? we examined variation in the nucleotide sequence of the mitochondri al control region (402 base pairs (bp) and the cytochrome b (cyt b) region (633 bp) in Norwegian and Siberian (Lemmus sibiricus) lemmings. The phyloge netic distinction and cyt b divergence estimate of 1.8% between the Norwegi an and Siberian lemmings suggest that their separation pre-dated the last g laciation and imply that the Norwegian lemming is probably a relic of the P leistocene populations from Western Europe. The star-like control region ph ylogeny; and low mitochondrial DNA diversity in the Norwegian lemming indic ate a reduction in its historical effective size followed by population exp ansion. The average estimate of post-bottleneck time (19-21kyr) is close to the last glacial maximum (18-22 kyr BP. Taking these findings and the foss il records into consideration, it seems: likely that. after colonization of Scandinavia in the Late Pleistocene, the Norwegian lemming suffered a redu ction in its population effective size and survived the last glacial maximu m in some local Scandinavian refugia, as suggested by early biogeographical work.