Synchronous genetic turnovers across Western Eurasia in Late Pleistocene collared lemmings

Abstract

Recent palaeogenetic studies indicate a highly dynamic history in collared lemmings (Dicrostonyx spp.), with several demographical changes linked to climatic fluctuations that took place during the last glaciation. At the western range margin of D. torquatus, these changes were characterized by a series of local extinctions and recolonizations. However, it is unclear whether this pattern represents a local phenomenon, possibly driven by ecological edge effects, or a global phenomenon that took place across large geographical scales. To address this, we explored the palaeogenetic history of the collared lemming using a next‐generation sequencing approach for pooled mitochondrial DNA amplicons. Sequences were obtained from over 300 fossil remains sampled across Eurasia and two sites in North America. We identified five mitochondrial lineages of D. torquatus that succeeded each other through time across Europe and western Russia, indicating a history of repeated population extinctions and recolonizations, most likely from eastern Russia, during the last 50 000 years. The observation of repeated extinctions across such a vast geographical range indicates large‐scale changes in the steppe‐tundra environment in western Eurasia during the last glaciation. All Holocene samples, from across the species' entire range, belonged to only one of the five mitochondrial lineages. Thus, extant D. torquatus populations only harbour a small fraction of the total genetic diversity that existed across different stages of the Late Pleistocene. In North American samples, haplotypes belonging to both D. groenlandicus and D. richardsoni were recovered from a Late Pleistocene site in south‐western Canada. This suggests that D. groenlandicus had a more southern and D. richardsoni a more northern glacial distribution than previously thought. This study provides significant insights into the population dynamics of a small mammal at a large geographical scale and reveals a rather complex demographical history, which could have had bottom‐up effects in the Late Pleistocene steppe‐tundra ecosystem.

Challenging the European southern refugium hypothesis: Species‐specific structures versus general patterns of genetic diversity and differentiation among small mammals

“…As such, for each glaciation that occurred, a substantial proportion of each species' lineage was lost, and with that its genetic heritage, complicating the interpretation of colonization patterns. The replacement of one phylogroup with another in line with climate oscillations has also been observed (Brace et al, 2012(Brace et al, , 2016Martínková et al, 2013;Palkopoulou et al, 2016;Searle et al, 2009) indicating that presentday genetic diversity alone can be insufficient to explain historical patterns (Hofreiter & Stewart, 2009;Searle et al, 2009). 2011;Stewart et al, 2010).…”

Implications and future prospects for evolutionary analyses of DNA in historical herbarium collections

“…Using herbarium specimens to study evolution, population history, and invasion When drawing conclusions about the evolutionary history of species, inferences are (Palkopoulou et al, 2016;Leonardi et al, 2017). Modern distribution of alleles and genotypes can therefore differ significantly from the past distribution.…”

Range shifts or extinction? Ancient DNA and distribution modelling reveal past and future responses to climate warming in cold‐adapted birds

“…Interestingly, these results have often shown that local extinctions and population turnovers, rather than survival by habitat tracking, were the dominant processes during past climate warming (e.g. Dal en et al, 2007;Lagerholm et al, 2014;Palkopoulou et al, 2016). This raises concerns from a conservation perspective, as such local extinctions following habitat loss could lead to ensuing losses of unique genetic variation.…”