Mutation and Recombination Rates in Free-Ranging Polar Bears

A pedigree-based study of Western Hudson Bay polar bears (Ursus maritimus) estimates a germline mutation rate of 1.22 × 10?? per site per generation and a recombination rate of 1.50 cM/Mb.

• Why it matters: Demographic and conservation analyses for polar bears have depended on mutation and recombination values borrowed from other mammals, where estimates can differ by an order of magnitude and propagate into downstream history inference.
• What they did: Using high-coverage whole-genome sequencing from eight parent-offspring trios, the team called 329 de novo mutations and phased meioses to measure 522 crossovers across 16 meioses, yielding 1.50 cM/Mb.
• The result: In 44 unrelated individuals from the same subpopulation, they inferred a demography-aware recombination map with a length-weighted genome-wide rate of 3.03 cM/Mb and identified 8,515 hotspot regions covering 2.10% of the genome.

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