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Evolutionary history of polar and brown bears

Hailer, Frank and Welch, Andreanna J 2016. Evolutionary history of polar and brown bears. eLS, Wiley-Blackwell, pp. 1-8. (10.1002/9780470015902.a0026303)

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Taxonomists have long recognised polar and brown bears as separate species with distinct ecological niches and largely nonoverlapping ranges. Surprisingly, phylogenetic studies of maternally inherited mitochondrial DNA (mtDNA) found polar bears nested within brown bears, with an estimated divergence time of <170 000 years. This indicated an unusually rapid speciation and adaptation of polar bears. However, several recent studies of autosomal and Y-chromosomal DNA have revisited these findings, giving independent perspectives of bear evolutionary history. Results show that polar bears cluster separately from brown bears, and divergence time estimates are older than those based on mtDNA, ranging from >300 000 to 4–5 million years. These studies confirm uniqueness of the polar bear lineage, provide more time for speciation and adaptation, and have uncovered numerous candidate genes for evolutionary adaptations. Several instances of introgressive hybridisation between polar and brown bears have been inferred, revealing trans-species transmission of mtDNA and some nuclear loci.

Item Type: Book Section
Status: Published
Schools: Biosciences
Subjects: Q Science > QH Natural history > QH426 Genetics
Q Science > QL Zoology
Uncontrolled Keywords: adaptation; arctic; genome sequencing; introgressive hybridization; mtDNA; Pleistocene; speciation; Ursus arctos; Ursus maritimus; Y chromosome
Publisher: Wiley-Blackwell
Last Modified: 06 Oct 2020 09:37

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