Mitochondrial DNA variation and the evolutionary history of chromosome races of collared lemmings (Dicrostonyx) in the Eurasian Arctic

Abstract

Collared lemmings (Dicrostonyx) demonstrate extensive chromosome variation along their circumpolar distribution in the high Arctic. To reveal the history of this genus and the origin of chromosome races in the Palearctic, we studied the geographical pattern of mtDNA variation in lemmings from 13 localities by using eight tetranucleotide restriction enzymes. The main split in mtDNA phylogeny is at the Bering Strait and corresponds to the main chromosome division between the Beringian and the Eurasian groups of karyotypes. Nucleotide divergence estimate of 6.8% suggests that, despite the Bering Land Bridge, Palearctic and Nearctic forms have been separated since the mid‐Pleistocene. Five distinct phylogenetic groups of mtDNA haplotypes, with average divergence of 1.5%, corresponding to geographical regions, were found along the Palearctic coast. Low nucleotide and haplotype diversity and a star‐like phylogeny within phylogeographical groups of haplotypes suggest regional bottleneck events in the recent past, most probably due to warming events during the Holocene. There is congruence between phylogeographical pattern of mtDNA variation and geographical distribution of chromosome races; 69% of the total mtDNA variation is allocated among chromosome races. This congruence implies that historical events such as fragmentation and allopatric bottleneck events have been important for the origin of chromosome races. However, historical factors do not explain the fixed autosome fusions found to distinguish certain populations.

Serial population extinctions in a small mammal indicate Late Pleistocene ecosystem instability

“…These lineages demonstrate the extensive genetic diversity of Late Pleistocene populations (Fig. S1), a distinct contrast to the genetically depauperate populations reported for this species at present (11). Ancient DNA studies have consistently reported postglacial loss of genetic diversity in northern Holarctic mammal species (12), including collared lemmings (13).…”

Refugia revisited: individualistic responses of species in space and time

“…Further evidence in support of the hypothesis has come from the study of fossil pollen, plant macros including wood charcoal, and mammals (Birks 2003;Willis & van During the last glaciation, many cold-adapted species had a larger distribution than they have today. Furthermore, several studies on cold-adapted species have identified genetic signatures of increase in population size during the early stages of the last glaciation, suggesting that these species had small population sizes also during the last interglacial (Fedorov et al 1999;Flagstad & Røed 2003;Shapiro et al 2004;Dalén et al 2005). It therefore seems likely that glacial expansions and interglacial contractions were a recurrent pattern for cold-adapted species during the Late Quaternary.…”

Terrestrial trophic dynamics in the Canadian Arctic

“…We have also included snap traps set for genetic analyses in places with indications of lemming activity (Fedorov et al 1999). This resulted in an average of 164 extra trap-nights at each site (range = 48-331, SD = 63).…”