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- Dehasque, Marianne, et al.
(författare)
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Temporal dynamics of woolly mammoth genome erosion prior to extinction
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A large number of species have recently recovered from near-extinction events. Understanding the genetic consequences of severe population declines followed by demographic recoveries is key to predict the long-term viability of species in order to mitigate future extinction risks. Although these species have avoided the immediate extinction threat, their long-term viability remains questionable due to the genetic consequences of population declines, which are not understood on a time scale beyond a few generations. The woolly mammoth (Mammuthus primigenius) population on Wrangel Island is an excellent model system to investigate long-term genetic consequences of a population bottleneck. Mammoths became isolated on the island in the early Holocene due to rising sea levels, and persisted for over 200 generations (~6,000 years) before becoming extinct ~4,000 years ago. To study the evolutionary processes leading up to the extinction of the woolly mammoth on the island, we analysed 21 Siberian woolly mammoth genomes, including that of one of the last known mammoths. Our results show that the Wrangel Island mammoths recovered quickly from an initially severe bottleneck, and subsequently remained demographically stable during the ensuing 6 millennia. Further, we find that highly deleterious mutations were gradually purged from the population, whereas there was an accumulation of mildly deleterious mutations. The gradual purging of highly deleterious mutations suggests an ongoing inbreeding depression that lasted for hundreds of generations. This time-lag between demographic and genetic recovery has wide-ranging implications for conservation management of recently bottlenecked present-day populations.
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| 2. |
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| 3. |
- van der Valk, Tom, et al.
(författare)
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Evolutionary consequences of genomic deletions and insertions in the woolly mammoth genome
- 2022
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Ingår i: iScience. - : Elsevier BV. - 2589-0042. ; 25:8
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Tidskriftsartikel (refereegranskat)abstract
- Woolly mammoths had a set of adaptations that enabled them to thrive in the Arctic environment. Many mammoth-specific single nucleotide polymorphisms (SNPs) responsible for unique mammoth traits have been previously identified from ancient genomes. However, a multitude of other genetic variants likely contributed to woolly mammoth evolution. In this study, we sequenced two woolly mammoth genomes and combined these with previously sequenced mammoth and elephant genomes to conduct a survey of mammoth-specific deletions and indels. We find that deletions are highly enriched in non-coding regions, suggesting selection against structural variants that affect protein sequences. Nonetheless, at least 87 woolly mammoth genes contain deletions or indels that modify the coding sequence, including genes involved in skeletal morphology and hair growth. These results suggest that deletions and indels contributed to the unique phenotypic adaptations of the woolly mammoth, and were potentially critical to surviving in its natural environment.
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| 4. |
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| 5. |
- van der Valk, Tom, et al.
(författare)
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Million-year-old DNA sheds light on the genomic history of mammoths
- 2021
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 591:7849, s. 265-269
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Tidskriftsartikel (refereegranskat)abstract
- Temporal genomic data hold great potential for studying evolutionary processes such as speciation. However, sampling across speciation events would, in many cases, require genomic time series that stretch well back into the Early Pleistocene subepoch. Although theoretical models suggest that DNA should survive on this timescale1, the oldest genomic data recovered so far are from a horse specimen dated to 780–560 thousand years ago2. Here we report the recovery of genome-wide data from three mammoth specimens dating to the Early and Middle Pleistocene subepochs, two of which are more than one million years old. We find that two distinct mammoth lineages were present in eastern Siberia during the Early Pleistocene. One of these lineages gave rise to the woolly mammoth and the other represents a previously unrecognized lineage that was ancestral to the first mammoths to colonize North America. Our analyses reveal that the Columbian mammoth of North America traces its ancestry to a Middle Pleistocene hybridization between these two lineages, with roughly equal admixture proportions. Finally, we show that the majority of protein-coding changes associated with cold adaptation in woolly mammoths were already present one million years ago. These findings highlight the potential of deep-time palaeogenomics to expand our understanding of speciation and long-term adaptive evolution.
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