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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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- Hasselgren, Malin, et al.
(författare)
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Genomic consequences of inbreeding and outbreeding in an endangered carnivore
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Loss of genetic variation through genetic drift and inbreeding is a major threat to small and isolated populations. Although previous studies have generally used genetically verified pedigrees to document effects of inbreeding and gene flow, these often fail to capture the whole inbreeding history. Also, empirical support for a link between genomic inbreeding and fitness is scarce. By sequencing complete genomes of 23 Scandinavian arctic foxes (Vulpes lagopus) born before and after an immigration event, we here look into the genomic consequences of inbreeding and genetic rescue. We found a significant difference, with 18% higher genome-wide heterozygosity and 81% lower genomic inbreeding in immigrant F1 compared to native individuals. However, more distant descendants of immigrants (F2, F3) did not show the same pattern. We also found that foxes surviving their first year generally had higher heterozygosity and lower inbreeding than non-survivors. Finally, pedigree-based inbreeding correlated with, but underestimated, genomic inbreeding levels. Our results demonstrate a fundamental link between genetic variation and fitness, the transient nature of genetic rescue, and that inbreeding is even more severe than captured from a genetically verified pedigree. Our results have important implications in conservation biology as inbreeding depression can be detected in populations lacking a pedigree.
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- Johannes, Måsviken, 1990-, et al.
(författare)
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Elevational variation of arthropod communities in the Swedish mountains
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Mountain topography gives rise to elevation gradients in both abiotic and biotic conditions, which can generate substantial biodiversity variation. Due to the close link between elevation and climate, mountain areas may be particularly useful for evaluating the ecological consequences of climate change. Arthropods are the most diverse animal phylum and play important roles in most ecosystems. Although arthropods are exposed to multiple stressors and are in global decline, we only have scant information on the distribution of arthropods along elevation gradients. We investigated how taxonomic richness, taxonomic composition, and spatial structuring of spider-, insect-, and springtail communities differed along elevation gradients at three sites in a high latitude mountain area. Taxonomic richness of spiders and insects declined monotonically with increasing elevation, but there were limited differences between sites in such declines. We did not observe any significant relationships between the taxonomic richness of springtails and elevation. Taxonomic composition did vary with elevation for all three taxonomic groups, and it also differed among the three sites. Spider- and insect communities were both spatially nested and showed spatial modularity along the elevation gradients. While the modular patterns suggest that species turnover has generated distinct communities at different elevations, some generalist species were still widespread throughout large parts of the gradients. We observed no spatial structuring in springtail communities along elevation gradients. Our results point to smaller differences among sites than among taxonomic groups in how taxonomic richness and community structuring varied with elevation. We interpret these results as support for taxonomically specific adaptations to environmental conditions being important for structuring arthropod communities. We also suggest that climate-driven changes to arthropod communities in mountain environments may be regulated by two not mutually exclusive processes, one in which generalist species may become more dominant and shift their ranges upward and one which high elevation specialists may go extinct because of increasingly fragmented habitats.
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