Population genetics of Ice Age brown bears

The Pleistocene was a dynamic period for Holarctic mammal species, complicated by episodes of glaciation, local extinctions, and intercontinental migration. The genetic consequences of these events are difficult to resolve from the study of present-day populations. To provide a direct view of population genetics in the late Pleistocene, we measured mitochondrial DNA sequence variation in seven permafrost-preserved brown bear (Ursus arctos) specimens, 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 any extant North American population, but by 15,000 years ago genetic diversity appears similar to the modern day. The older, genetically diverse, Beringian population contained sequences from three clades now restricted to local regions within North America, indicating that current phylogeographic patterns may provide misleading data for evolutionary studies and conservation management. The late Pleistocene phylogeographic data also indicate possible colonization routes to areas south of the Cordilleran ice sheet.

(Table S2) Biometric data, time of ice breakup and carbon isotopic composition of adipose tissue of polar bears (Ursus maritimus) between 1991-2007

Two global environmental issues, climate change and contamination by persistent organic pollutants, represent major concerns for arctic ecosystems. Yet, it is unclear how these two stressors interact in the Arctic. For instance, the influence of climate-associated changes in food web structure on exposure to pollutants within arctic ecosystems is presently unknown. Here, we report on recent changes in feeding ecology (1991-2007) in polar bears (Ursus maritimus) from the western Hudson Bay subpopulation that have resulted in increases in the tissue concentrations of several chlorinated and brominated contaminants. Differences in timing of the annual sea ice breakup explained a significant proportion of the diet variation among years. As expected from climate change predictions, this diet change was consistent with an increase in the consumed proportions of open water-associated seal species compared to ice-associated seal species in years of earlier sea ice breakup. Our results demonstrate that climate change is a modulating influence on contaminants in this polar bear subpopulation and may pose an additional and previously unidentified threat to northern ecosystems through altered exposures to contaminants.

The Blackwater chronicle : a narrative of an expedition into the land of Canaan, in Randolph county, Virginia, a country flowing with wild animals, such as panthers, bears, wolves, elk, deer, otter, badger, &c., &c., with innumerable trout--by five adventurous gentlemen, without any aid of government, and solely by their own resources, in the summer of 1851 /

Generally attributed to John Pendleton Kennedy, brother of the author. cf. H.T. Tuckerman, Life of J.P. Kennedy, 1871, p. 26 and 421.

Twenty years among the bulls and bears of Wall street.

Mode of access: Internet.

Uncle Tom Andy Bill : a story of bears and Indian treasure /

Frontispiece illustrated by P.V.E. Ivory.

Bears in the Yellowstone,

"List of Yellowstone park animals": p. 143-151.

Book of a hundred bears,

Mode of access: Internet.

How to live with black bears /

"HT-66"--P. [8].