Finland’s brown bears on surprise fast track to recover diversity

Once near extinction, Finland’s brown bears are defying expectations in how quickly they are regaining the genetic underpinnings of a healthy population.

In just a generation and a half, the nation’s southern bears have reached a level of genetic diversity and population mixing that theorists predict would typically take 10 generations or more, researchers say April 22 in Proceedings of the Royal Society B.

From 1996 through 2010, the once rather isolated southern bear group expanded its range north about 7.4 kilometers per year on average. That spread allowed them to mix more with high-latitude brown bears. In southern Finland, the brown bears also now mingle freely with a growing number of Russian counterparts adventuring over the border. These encounters very likely helped fuel a surge in genetic diversity among the southern Finnish bears, says study coauthor Snorre Hagen of the Norwegian Institute for Agricultural and Environmental Research in Svanvik.

Hagen and colleagues pieced together the bear comeback story by tracing 12 genetic markers in samples from 819 Ursus arctos bears. Most samples came from a frozen trove of tissue samples that wildlife managers saved from legally killed bears. Chances have risen about 8 percent that southern bears will inherit different (heterozygous) versions of DNA markers from mom versus dad, researchers found.

A mix of expanding range and Russian influx has apparently boosted the bears’ prospects. Their current comeback, from an estimated low of 150 individuals in 1963 to about 1,700, could change the way conservationists weigh options for genetic restoration, Hagen muses.