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High genetic variability of vagrant polar bears illustrates importance of population connectivity in fragmented sea ice habitats

Kutschera, V. E.; Frosch, C.; Janke, A. LU ; Skírnisson, K.; Bidon, T.; Lecomte, N.; Fain, S. R.; Eiken, H. G.; Hagen, S. B. and Arnason, U. LU , et al. (2016) In Animal Conservation 19(4). p.337-349
Abstract

Projections by the Intergovernmental Panel on Climate Change (IPCC) and sea ice forecasts suggest that Arctic sea ice will decline markedly in coming decades. Expected effects on the entire ecosystem include a contraction of suitable polar bear habitat into one or few refugia. Such large-scale habitat decline and fragmentation could lead to reduced genetic diversity. Here we compare genetic variability of four vagrant polar bears that reached Iceland with that in recognized subpopulations from across the range, examining 23 autosomal microsatellites, mitochondrial control region sequences and Y-chromosomal markers. The vagrants' genotypes grouped with different genetic clusters and showed similar genetic variability at autosomal... (More)

Projections by the Intergovernmental Panel on Climate Change (IPCC) and sea ice forecasts suggest that Arctic sea ice will decline markedly in coming decades. Expected effects on the entire ecosystem include a contraction of suitable polar bear habitat into one or few refugia. Such large-scale habitat decline and fragmentation could lead to reduced genetic diversity. Here we compare genetic variability of four vagrant polar bears that reached Iceland with that in recognized subpopulations from across the range, examining 23 autosomal microsatellites, mitochondrial control region sequences and Y-chromosomal markers. The vagrants' genotypes grouped with different genetic clusters and showed similar genetic variability at autosomal microsatellites (expected heterozygosity, allelic richness, and individual heterozygosity) as individuals in recognized subpopulations. Each vagrant carried a different mitochondrial haplotype. A likely route for polar bears to reach Iceland is via Fram Strait, a major gateway for the physical exportation of sea ice from the Arctic basin. Vagrant polar bears on Iceland likely originated from more than one recognized subpopulation, and may have been caught in sea ice export during long-distance movements to the East Greenland area. Although their potentially diverse geographic origins might suggest that these vagrants encompass much higher genetic variability than vagrants or dispersers in other regions, the four Icelandic vagrants encompassed similar genetic variability as any four randomly picked individuals from a single subpopulation or from the entire sample. We suggest that this is a consequence of the low overall genetic variability and weak range-wide genetic structuring of polar bears – few dispersers can represent a large portion of the species' gene pool. As predicted by theory and our demographic simulations, continued gene flow will be necessary to counteract loss of genetic variability in increasingly fragmented Arctic habitats. Similar considerations will be important in the management of other taxa that utilize sea ice habitats.

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published
subject
keywords
Arctic sea ice, climate change, dispersal, genetic variability, habitat fragmentation, inbreeding, polar bear, Ursus maritimus
in
Animal Conservation
volume
19
issue
4
pages
13 pages
publisher
Cambridge University Press
external identifiers
  • scopus:84954446410
  • wos:000381208400006
ISSN
1367-9430
DOI
10.1111/acv.12250
language
English
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yes
id
6a1522ed-3b78-4598-b42f-3784c2eb5123
date added to LUP
2017-01-12 09:05:09
date last changed
2017-09-18 11:36:11
@article{6a1522ed-3b78-4598-b42f-3784c2eb5123,
  abstract     = {<p>Projections by the Intergovernmental Panel on Climate Change (IPCC) and sea ice forecasts suggest that Arctic sea ice will decline markedly in coming decades. Expected effects on the entire ecosystem include a contraction of suitable polar bear habitat into one or few refugia. Such large-scale habitat decline and fragmentation could lead to reduced genetic diversity. Here we compare genetic variability of four vagrant polar bears that reached Iceland with that in recognized subpopulations from across the range, examining 23 autosomal microsatellites, mitochondrial control region sequences and Y-chromosomal markers. The vagrants' genotypes grouped with different genetic clusters and showed similar genetic variability at autosomal microsatellites (expected heterozygosity, allelic richness, and individual heterozygosity) as individuals in recognized subpopulations. Each vagrant carried a different mitochondrial haplotype. A likely route for polar bears to reach Iceland is via Fram Strait, a major gateway for the physical exportation of sea ice from the Arctic basin. Vagrant polar bears on Iceland likely originated from more than one recognized subpopulation, and may have been caught in sea ice export during long-distance movements to the East Greenland area. Although their potentially diverse geographic origins might suggest that these vagrants encompass much higher genetic variability than vagrants or dispersers in other regions, the four Icelandic vagrants encompassed similar genetic variability as any four randomly picked individuals from a single subpopulation or from the entire sample. We suggest that this is a consequence of the low overall genetic variability and weak range-wide genetic structuring of polar bears – few dispersers can represent a large portion of the species' gene pool. As predicted by theory and our demographic simulations, continued gene flow will be necessary to counteract loss of genetic variability in increasingly fragmented Arctic habitats. Similar considerations will be important in the management of other taxa that utilize sea ice habitats.</p>},
  author       = {Kutschera, V. E. and Frosch, C. and Janke, A. and Skírnisson, K. and Bidon, T. and Lecomte, N. and Fain, S. R. and Eiken, H. G. and Hagen, S. B. and Arnason, U. and Laidre, K. L. and Nowak, C. and Hailer, F.},
  issn         = {1367-9430},
  keyword      = {Arctic sea ice,climate change,dispersal,genetic variability,habitat fragmentation,inbreeding,polar bear,Ursus maritimus},
  language     = {eng},
  month        = {08},
  number       = {4},
  pages        = {337--349},
  publisher    = {Cambridge University Press},
  series       = {Animal Conservation},
  title        = {High genetic variability of vagrant polar bears illustrates importance of population connectivity in fragmented sea ice habitats},
  url          = {http://dx.doi.org/10.1111/acv.12250},
  volume       = {19},
  year         = {2016},
}