Phylogeography of lemmings (Lemmus): no evidence for postglacial colonization of Arctic from the Beringian refugium

Abstract

Beringia is considered as an important glacial refugium that served as the main source for colonization of formerly glaciated Arctic regions. To obtain high resolution views of Arctic refugial history, we examined mitochondrial cytochrome b phylogeography in the northern genus of rodents, Lemmus (true lemmings), sampled across its circumpolar distribution. Strong phylogeographical structure suggests vicariant separation over several glacial-interglacial periods and does not provide evidence supporting the importance of Beringia for extensive colonization of formerly glaciated regions. Rather than a source of postglacial colonization, Beringia represents an area of intraspecific endemism previously undetected by biogeographical analysis. Existing phylogeographical structure suggests that vicariant separation by glacial barriers was an important factor generating genetic divergence and, thus, increasing genetic diversity in lemmings on continental and circumpolar scales. However, there is little evidence for the direct effect of the last glaciation on the level of genetic variation and allele genealogy in lemmings on a regional geographical scale. This finding implies that the population genetic models of postglacial colonization suggested for temperate taxa might have limited applicability for Arctic species.

Population genetic structure of North American burbot (Lota lota maculosa) across the Nearctic and at its contact zone with Eurasian burbot (Lota lota lota)

“…Note that the microsatellite admixture is calculated at the population level, while mtDNA admixture refers to the frequency of Lota l. lota (EB lineage) or L. l. maculosa (NA lineage) mtDNA in individuals in the population. Rhymer et al 2001;Fedorov et al 2003), though subspecies of closely related temperate fish are often found to interbreed freely at contact zones (reviewed in Utter 2001;Lutz-Carrillo et al 2006;Taylor et al 2007). In fact, interbreeding when no geographic barrier prevails is fundamental to the definition of fish subspecies (Nelson 1999;Haig et al 2006).…”

Phylogeography and environmental diversification of a highly adaptable marine amphipod, Gammarus duebeni

“…For G. d. duebeni, molecular diversity is low with haplotypes shared across broad geographic areas, including the coasts of both N America and Europe. Such a pattern is indicative of taxa experiencing postglacial expansion (Ibrahim et al, 1996;Hewitt, 2000;Fedorov et al, 2003;Lessa et al, 2003). A degree of genetic differentiation does exist among some populations, most noticeably at the species' latitudinal extremes (e.g.…”

“…However, because our data indicates a very recent common ancestor for amphi-Atlantic populations, it seems unlikely that it has in fact persisted in northern areas throughout the Pleistocene. Study of such northern and cold-tolerant taxa is potentially a productive direction for phylogeographic studies aimed at better understanding the response of communities to climate cycles (Fedorov et al, 2003;Hewitt, 2004).…”

Genetic structuring in three closely related circumpolar plant species: AFLP versus microsatellite markers and high-arctic versus arctic–alpine distributions

“…Considerable geographic structuring of the genetic diversity has been identified in all of them. Distinct phylogeographic structuring has also been observed in many arctic animals, for example, Lemmus spp., Daphnia pulex and Calidris alpina (Weider et al, 1999;Wennerberg, 2001;Federov et al, 2003). However, in some arctic animals, such as the polar fox , the polar bear (Paetkau et al, 1999) and the snowy owl (Marthinsen et al, 2008), there is surprisingly little geographic structuring of the genetic diversity even at the vast circumpolar scale.…”