title: Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage.
abstract: Recent studies have shown that the polar bear matriline (mitochondrial DNA) evolved from a brown bear lineage since the late Pleistocene, potentially indicating rapid speciation and adaption to arctic conditions. Here, we present a high-resolution data set from multiple independent loci across the nuclear genomes of a broad sample of polar, brown, and black bears. Bayesian coalescent analyses place polar bears outside the brown bear clade and date the divergence much earlier, in the middle Pleistocene, about 600 (338 to 934) thousand years ago. This provides more time for polar bear evolution and confirms previous suggestions that polar bears carry introgressed brown bear mitochondrial DNA due to past hybridization. Our results highlight that multilocus genomic analyses are crucial for an accurate understanding of evolutionary history.
authors.affiliation: Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25, 60325 Frankfurt am Main, Germany. frashai@gmx.net
authors.forename: Frank
authors.initials: F
authors.lastname: Hailer
authors.forename: Verena E
authors.initials: VE
authors.lastname: Kutschera
authors.forename: Björn M
authors.initials: BM
authors.lastname: Hallström
authors.forename: Denise
authors.initials: D
authors.lastname: Klassert
authors.forename: Steven R
authors.initials: SR
authors.lastname: Fain
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Leonard
authors.forename: Ulfur
authors.initials: U
authors.lastname: Arnason
authors.forename: Axel
authors.initials: A
authors.lastname: Janke
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D051456:Gene Flow; D049810:Genetic Speciation; D014644:Genetic Variation; D016678:Genome; D006239:Haplotypes; D006824:Hybridization, Genetic; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D001503:Ursidae / Q000145:classification / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial