Both gender and movement important for genetic diversity of grizzly bears.

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Grizzly bears in the southern portion of the Northern Continental Divide Ecosystem experienced a rapid increase in genetic diversity, according to a new study led by the USGS.

Mother grizzly and cub at Gibbon River, Yellowstone National Park.
A USGS grizzly bear researcher snapped this picture of a mother grizzly bear and her cub in Yellowstone National Park. Adult females are the most important segment of the grizzly bear populations because they are the reproductive engine.Frank van Manen, USGS

Using long-term, ecosystem-scale research to build a grizzly bear family tree, this project found that individual-level reproductive dynamics and dispersal can have dramatic effects on the spatial patterns of genetic diversity. 

The study found that a few reproductively dominant individuals (over 100 descendants for a single adult male) led to lower genetic diversity in peripheral regions of the population, and that genetic diversity increased rapidly (in less than one generation) during recent population expansion, concurrent with increased dispersal into the peripheral regions.   Together, this demonstrates that individuals can have immense impacts on patterns in genetic variation across expansive landscapes, resulting in highly ephemeral patterns in genetic diversity.

This work illustrates the importance of preserving habitat and connecting even semi-isolated remnant groups of animals and is consistent with other research that the population of grizzly bears in the Northern Continental Divide Ecosystem, currently listed as threatened, is recovering.

This is the first known research on grizzly bears to document the mechanism behind changes in genetic diversity in an expanding population.  

The paper, “Demographic mechanisms underpinning genetic assimilation of remnant groups of a large carnivore” was published in The Proceedings of the Royal Society B and can be found HERE.

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