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Data from: "Polar bear (Ursus maritimus) transcriptome assembly and SNP discovery" in Genomic Resources Notes accepted 1 August 2013-30 September 2013
Malenfant, René M.; Coltman, David L.; Richardson, Evan S.; Lunn, Nicholas J.; Davis, Corey S.; Coltman, David W.; Lunn, Nick J. — 2013-11-12 Polar bears (Ursus maritimus) in the Western Hudson Bay subpopulation have been declining in size and body condition for decades, as climate change causes earlier sea ice breakup, reduced hunting time on the ice, and an increasingly long fasting season. As Western Hudson Bay females have decreased in size, rates of litter production and average litter size have also decreased, while cub mortality and average time to independence have increased. Although these changes have potential evolutionary consequences, little is yet known about the adaptive genetic variation in body size or fat accumulation that would have to underlie any such change. In this study, we used high-throughput Illumina sequencing to develop SNPs from pooled blood and fat transcriptomes, using samples from five adult female polar bears and five (unrelated) dependent cubs. In total, we generated 371,258 transcripts of which 36,755 were deemed to be “full length” (i.e., covered more than 90% of their best BLAST hit), and we identified 63,020 SNPs. Since this study was conducted, we have used a subset of these SNPs to develop an Illumina BeadArray for quantitative genetics research in Western Hudson Bay.
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Data from: Heritability of body size in the polar bears of Western Hudson Bay
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Malenfant, René M.; Davis, Corey S.; Richardson, Evan S.; Lunn, Nicholas J.; Coltman, David W. — 2022-04-26 Among polar bears (Ursus maritimus), fitness is dependent on body size through males' abilities to win mates, females' abilities to provide for their young, and all bears' abilities to survive increasingly longer fasting periods caused by climate change. In the Western Hudson Bay subpopulation (near Churchill, Manitoba, Canada), polar bears have declined in body size and condition, but nothing is known about the genetic underpinnings of body size variation, which may be subject to natural selection. Here, we combine a 4449-individual pedigree and an array of 5433 single-nucleotide polymorphisms (SNPs) to provide the first quantitative genetics study of polar bears. We used animal models to estimate heritability (h2) among polar bears handled between 1966 and 2011, obtaining h2 estimates of 0.34-0.48 for strictly skeletal traits and 0.18 for axillary girth (which is also dependent on fatness). We genotyped 859 individuals with the SNP array to test for marker-trait association and combined p-values over genetic pathways using gene-set analysis. Variation in all traits appeared to be polygenic, but we detected one region of moderately large effect size in body length near a putative noncoding RNA in an unannotated region of the genome. Gene-set analysis suggested that variation in body length was associated with genes in the regulatory cascade of cyclin expression, which has previously been associated with body size in mice. A greater understanding of the genetic architecture of body size variation will be valuable in understanding the potential for adaptation in polar bear populations challenged by climate change.

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(auteur : Lunn, Nicholas J.)

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