On the origin of the Norwegian lemming.

The Pleistocene glacial cycles resulted in significant changes in species distributions, and it has been discussed whether this caused increased rates of population divergence and speciation. One species that is likely to have evolved during the Pleistocene is the Norwegian lemming (Lemmus lemmus). However, the origin of this species, both in terms of when and from what ancestral taxon it evolved, has been difficult to ascertain. Here, we use ancient DNA recovered from lemming remains from a series of Late Pleistocene and Holocene sites to explore the species' evolutionary history. The results revealed considerable genetic differentiation between glacial and contemporary samples. Moreover, the analyses provided strong support for a divergence time prior to the Last Glacial Maximum (LGM), therefore likely ruling out a postglacial colonization of Scandinavia. Consequently, it appears that the Norwegian lemming evolved from a small population that survived the LGM in an ice-free Scandinavian refugium

The Western Ontario Shoulder Instability Index (WOSI): validity, reliability, and responsiveness retested with a Swedish translation

Background and purpose The WOSI score questionnaire is a tool designed for self-assessment of shoulder function for patients with instability problems. We made a translation into Swedish and retested the score by analyzing the psychometric properties validity, reliability, and responsiveness

Genomic Consequences of Fragmentation in the Endangered Fennoscandian Arctic Fox (Vulpes lagopus)

Accelerating climate change is causing severe habitat fragmentation in the Arctic, threatening the persistence of many cold-adapted species. The Scandinavian arctic fox (V. lagopus) is highly fragmented, with a once continuous, circumpolar distribution, it struggled to recover from a demographic bottleneck in the late 19th century. The future persistence of the entire Scandinavian population is highly dependent on the northernmost Fennoscandian subpopulations (Scandinavia and the Kola Peninsula), to provide a link to the viable Siberian population. By analyzing 43 arctic fox genomes, we quantified genomic variation and inbreeding in these populations. Signatures of genome erosion increased from Siberia to northern Sweden indicating a stepping-stone model of connectivity. In northern Fennoscandia, runs of homozygosity (ROH) were on average ~1.47-fold longer than ROH found in Siberia, stretching almost entire scaffolds. Moreover, consistent with recent inbreeding, northern Fennoscandia harbored more homozygous deleterious mutations, whereas Siberia had more in heterozygous state. This study underlines the value of documenting genome erosion following population fragmentation to identify areas requiring conservation priority. With the increasing fragmentation and isolation of Arctic habitats due to global warming, understanding the genomic and demographic consequences is vital for maintaining evolutionary potential and preventing local extinctions. inbreeding; runs of homozygosity; bottleneck; fragmentation; mutational load; conservatio

Ancient reindeer mitogenomes reveal island-hopping colonisation of the Arctic archipelagos

Climate warming at the end of the last glacial period had profound effects on the distribution of cold-adapted species. As their range shifted towards northern latitudes, they were able to colonise previously glaciated areas, including remote Arctic islands. However, there is still uncertainty about the routes and timing of colonisation. At the end of the last ice age, reindeer/caribou (Rangifer tarandus) expanded to the Holarctic region and colonised the archipelagos of Svalbard and Franz Josef Land. Earlier studies have proposed two possible colonisation routes, either from the Eurasian mainland or from Canada via Greenland. Here, we used 174 ancient, historical and modern mitogenomes to reconstruct the phylogeny of reindeer across its whole range and to infer the colonisation route of the Arctic islands. Our data shows a close affinity among Svalbard, Franz Josef Land and Novaya Zemlya reindeer. We also found tentative evidence for positive selection in the mitochondrial gene ND4, which is possibly associated with increased heat production. Our results thus support a colonisation of the Eurasian Arctic archipelagos from the Eurasian mainland and provide some insights into the evolutionary history and adaptation of the species to its High Arctic habitat

Genomic basis for skin phenotype and cold adaptation in the extinct Steller’s sea cow

Steller’s sea cow, an extinct sirenian and one of the largest Quaternary mammals, was described by Georg Steller in 1741 and eradicated by humans within 27 years. Here, we complement Steller’s descriptions with paleogenomic data from 12 individuals. We identified convergent evolution between Steller’s sea cow and cetaceans but not extant sirenians, suggesting a role of several genes in adaptation to cold aquatic (or marine) environments. Among these are inactivations of lipoxygenase genes, which in humans and mouse models cause ichthyosis, a skin disease characterized by a thick, hyperkeratotic epidermis that recapitulates Steller’s sea cows’ reportedly bark-like skin. We also found that Steller’s sea cows’ abundance was continuously declining for tens of thousands of years before their description, implying that environmental changes also contributed to their extinction

Nonreceding hare lines: genetic continuity since the Late Pleistocene in European mountain hares (Lepus timidus)

Throughout time, climate changes have caused substantial rearrangements of habitats which have alternately promoted and disfavoured different types of taxa. At first glance, the mountain hare (Lepus timidus) shows the typical hallmarks of a cold-adapted species that has retreated to refugia since the onset of the current Holocene interglacial. In contrary to expectations, however, the species has a high contemporary genetic diversity with no clear differentiation between geographically isolated populations. In order to clarify the phylogeographic history of European mountain hares, we here analysed ancient DNA from the glacial populations that inhabited the previous midlatitude European tundra region. Our results reveal that the Ice Age hares had similar levels of genetic variation and lack of geographic structure as observed today, and the ancient samples were intermingled with modern individuals throughout the reconstructed evolutionary tree. This suggest a temporal genetic continuity in Europe, where the mountain hares were able to keep pace with the rapid changes at the last glacial/interglacial transition, and successfully track their shifting habitat to northern and alpine regions. Further, the temporal demographic analyses showed that the species’ population size in Europe appear to have been tightly linked with palaeoclimatic fluctuations, with increases and declines occurring during periods of global cooling and warming, respectively. Taken together, our results suggest that neither habitat shifts nor demographic fluctuations have had any substantial impact on the genetic diversity of European mountain hares. This remarkable resilience, which contrasts to a majority of previously investigated cold-adapted species, is likely due to its generalist nature which makes it less vulnerable to environmental changes

Genomic insights into the conservation status of the world’s last remaining Sumatran rhinoceros populations

Highly endangered species like the Sumatran rhinoceros are at risk from inbreeding. Five historical and 16 modern genomes from across the species range show mutational load, but little evidence for local adaptation, suggesting that future inbreeding depression could be mitigated by assisted gene flow among populations. Small populations are often exposed to high inbreeding and mutational load that can increase the risk of extinction. The Sumatran rhinoceros was widespread in Southeast Asia, but is now restricted to small and isolated populations on Sumatra and Borneo, and most likely extinct on the Malay Peninsula. Here, we analyse 5 historical and 16 modern genomes from these populations to investigate the genomic consequences of the recent decline, such as increased inbreeding and mutational load. We find that the Malay Peninsula population experienced increased inbreeding shortly before extirpation, which possibly was accompanied by purging. The populations on Sumatra and Borneo instead show low inbreeding, but high mutational load. The currently small population sizes may thus in the near future lead to inbreeding depression. Moreover, we find little evidence for differences in local adaptation among populations, suggesting that future inbreeding depression could potentially be mitigated by assisted gene flow among populations

Muscle strength, gait, and balance in 20 patients with hip osteoarthritis followed for 2 years after THA

Background Patients with hip osteoarthritis (OA) have muscular weakness, impaired balance, and limp. Deficits in the different limb muscles and their recovery courses are largely unknown, however. We hypothesized that there is persisting muscular weakness in lower limb muscles and an impaired balance and gait 2 years after THA