Population genetics of Ice age brown bears

The Pleistocene was a dynamic period for Holarctic mammal species, complica ted by episodes of glaciation, local extinctions, and intercontinental migr ation. The genetic consequences of these events are difficult to resolve fr om the study of present-day populations. To provide a direct view of popula tion genetics in the late Pleistocene, we measured mitochondrial DNA sequen ce variation in seven permafrost-preserved brown bear (Ursus arctos) specim ens, dated from 14,000 to 42,000 years ago. Approximately 36,000 years ago, the Beringian brown bear population had a higher genetic diversity than an y extant North American population, but by 15,000 years ago genetic diversi ty appears similar to the modern day. The older, genetically diverse. Berin gian population contained sequences from three clades now restricted to loc al regions within North America, indicating that current phylogeographic pa tterns may provide misleading data for evolutionary studies and conservatio n management. The late Pleistocene phylogeographic data also indicate possi ble colonization routes to areas south of the Cordilleran ice sheet.