Bear-hybrids: behaviour and phenotype

Preuss, André; Gansloßer, Udo; Purschke, Günter; Magiera, Ute

doi:10.1016/j.zoolgart.2009.08.005

Cited by 16 publications

(12 citation statements)

References 2 publications

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“…Miller and colleagues concluded that the lineage that would become polar bears diverged from that which would become brown bears more than 4 million years ago, followed by admixture that continues to the present [6]. Consistent with this, the past and present geographic ranges of both species overlap at their margins (Figure 1), and fertile hybrids are known in both captive and wild populations [2], [12].…”

Section: Introductionmentioning

confidence: 93%

Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution

et al. 2013

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Despite extensive genetic analysis, the evolutionary relationship between polar bears (Ursus maritimus) and brown bears (U. arctos) remains unclear. The two most recent comprehensive reports indicate a recent divergence with little subsequent admixture or a much more ancient divergence followed by extensive admixture. At the center of this controversy are the Alaskan ABC Islands brown bears that show evidence of shared ancestry with polar bears. We present an analysis of genome-wide sequence data for seven polar bears, one ABC Islands brown bear, one mainland Alaskan brown bear, and a black bear (U. americanus), plus recently published datasets from other bears. Surprisingly, we find clear evidence for gene flow from polar bears into ABC Islands brown bears but no evidence of gene flow from brown bears into polar bears. Importantly, while polar bears contributed <1% of the autosomal genome of the ABC Islands brown bear, they contributed 6.5% of the X chromosome. The magnitude of sex-biased polar bear ancestry and the clear direction of gene flow suggest a model wherein the enigmatic ABC Island brown bears are the descendants of a polar bear population that was gradually converted into brown bears via male-dominated brown bear admixture. We present a model that reconciles heretofore conflicting genetic observations. We posit that the enigmatic ABC Islands brown bears derive from a population of polar bears likely stranded by the receding ice at the end of the last glacial period. Since then, male brown bear migration onto the island has gradually converted these bears into an admixed population whose phenotype and genotype are principally brown bear, except at mtDNA and X-linked loci. This process of genome erosion and conversion may be a common outcome when climate change or other forces cause a population to become isolated and then overrun by species with which it can hybridize.

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Section: Introductionmentioning

confidence: 93%

Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution

et al. 2013

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“…In addition, polar bears and brown bears produce viable and fertile hybrids both in the wild and in captivity (Preuß et al . ; Stirling ), suggesting a recent divergence between the two lineages.…”

Section: Introductionmentioning

confidence: 98%

“…At many loci, lineages have not yet sorted between the two species (Hailer et al 2012(Hailer et al , 2013Cahill et al 2013), which complicates estimates of when the two species diverged. In addition, polar bears and brown bears produce viable and fertile hybrids both in the wild and in captivity (Preuß et al 2009;Stirling 2011), suggesting a recent divergence between the two lineages.…”

Section: Introductionmentioning

confidence: 99%

Genomic evidence of geographically widespread effect of gene flow from polar bears into brown bears

et al. 2015

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Polar bears are an arctic, marine adapted species that is closely related to brown bears. Genome analyses have shown that polar bears are distinct and genetically homogeneous in comparison to brown bears. However, these analyses have also revealed a remarkable episode of polar bear gene flow into the population of brown bears that colonized the Admiralty, Baranof and Chichagof islands (ABC islands) of Alaska. Here, we present an analysis of data from a large panel of polar bear and brown bear genomes that includes brown bears from the ABC islands, the Alaskan mainland and Europe. Our results provide clear evidence that gene flow between the two species had a geographically wide impact, with polar bear DNA found within the genomes of brown bears living both on the ABC islands and in the Alaskan mainland. Intriguingly, while brown bear genomes contain up to 8.8% polar bear ancestry, polar bear genomes appear to be devoid of brown bear ancestry, suggesting the presence of a barrier to gene flow in that direction.

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“…Polar bears are carnivorous and only pregnant females hibernate, whereas brown bears are omnivorous and both sexes hibernate. The species can hybridize in captivity, and 2 cases of interbreeding in the wild have been observed (Kowalska 1969;Gray 1972;Doupé et al 2007;Preuß et al 2009;Stirling 2011). It has been hypothesized that climate change-induced changes to polar bear habitat could increase contact and potential hybridization between the species (Kelly et al 2010).…”

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confidence: 99%

Genetic Relationships of Extant Brown Bears (Ursus arctos) and Polar Bears (Ursus maritimus)

Cronin¹,

MacNeil

2012

Journal of Heredity

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Data deposited at Dryad: http://dx.doi.org/10.5061/dryad.q30rt Polar bears (Ursus maritimus) and brown bears (Ursus arctos) are closely related species for which extensive mitochondrial and nuclear phylogenetic comparisons have been made. We used previously published genotype data for 8 microsatellite DNA loci from 930 brown bears in 19 populations and 473 polar bears in 16 populations to compare the population genetic relationships of extant populations of the species. Genetic distances (Nei standard distance = 1.157), the proportion of private alleles (52% of alleles are not shared by the species), and Bayesian cluster analysis are consistent with morphological and life-history characteristics that distinguish polar bears and brown bears as different species with little or no gene flow among extant populations.

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Bear-hybrids: behaviour and phenotype

Cited by 16 publications

References 2 publications

Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution

Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution

Genomic evidence of geographically widespread effect of gene flow from polar bears into brown bears

Genetic Relationships of Extant Brown Bears (Ursus arctos) and Polar Bears (Ursus maritimus)

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