Ancient Hybridization and an Irish Origin for the Modern Polar Bear Matriline

Ceiridwen Edwards, Marc Suchard, Philippe Lemey, John Welch, Ian Barnes, Tara Fulton, Ross Barnett, Tamsin O'Connell, Pete Coxon, Nigel Monaghan, Cris Valdiosera, Eline Lorenzen, Eske Willerslev, Gennady Baryshnikov, Mark Thomas, Daniel Bradley, Beth Shapiro

Research output: Contribution to journalArticlepeer-review


Polar bears (Ursus maritimus) are among those species most susceptible to the rapidly changing arctic climate, and their survival is of global concern. Despite this, little is known about polar bear species history. Future conservation strategies would significantly benefit from an understanding of basic evolutionary information, such as the timing and conditions of their initial divergence from brown bears (U. arctos) or their response to previous environmental change.
We used a spatially explicit phylogeographic model to estimate the dynamics of 242 brown bear and polar bear matrilines sampled throughout the last 120,000 years and across their present and past geographic ranges. Our results show that the present distribution of these matrilines was shaped by a combination of regional stability and rapid, long-distance dispersal from ice-age refugia. In addition, hybridization between polar bears and brown bears may have occurred multiple times throughout the Late Pleistocene.
The reconstructed matrilineal history of brown and polar bears has two striking features. First, it is punctuated by dramatic and discrete climate-driven dispersal events. Second, opportunistic mating between these two species as their ranges overlapped has left a strong genetic imprint. In particular, a likely genetic exchange with extinct Irish brown bears forms the origin of the modern polar bear matriline. This suggests that interspecific hybridization not only may be more common than previously considered but may be a mechanism by which species deal with marginal habitats during periods of environmental deterioration.
Polar bears and brown bears have been hybridizing throughout the last 100,000 years
The current polar bear matriline descends from brown bears that lived near Ireland
This matriline most likely originated prior to or during the last ice age
The dynamics of bear matrilines have been driven by largely by climate change
Original languageEnglish
Pages (from-to)1251-1258
JournalCurrent Biology
Issue number15
Publication statusPublished - 9 Aug 2011

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