Genomic study clarifies brown bear diversity across species range
A new genomic study has mapped the genetic diversity of brown bears across their entire species range. The research reveals the impact of the last ice age on current bear population structures and divergence.
Scientists from the Senckenberg Centre for Human Evolution and Palaeoenvironment were part of an international team that investigated the genetic diversity of brown bears (Ursus arctos) and the historical factors that shaped it. Published in "Communications Biology," the study presents the first comprehensive population genomic analysis of the species and specifically clarifies the effects of the last ice age on its current structure and divergence.
Brown bears are found across North America, Europe, Russia, and Asia. While the global population is estimated at around 200,000 individuals, European populations have significantly declined since the Middle Ages due to habitat destruction and hunting. The study analyzed the genomes of 128 brown bears from across the species' range to test previous findings on similarities and differences between various populations.
Genetic analyses partially confirmed the current subspecies classification of brown bears, particularly for populations in Europe and Western Russia. For example, all bears in these regions, including those in the Ural Mountains and Western Siberia, genetically belong to the same group, the Eurasian brown bear (Ursus arctos arctos), despite vast geographical distances.
However, the study revealed an unexpected finding regarding North American bears. The brown bear of the Alaska Peninsula (Ursus arctos gyas) was found to be genetically closer to the Kodiak bear (Ursus arctos middendorffi) than to the more commonly known grizzly bear (Ursus arctos horribilis). This result could lead to a reassessment of the subspecies classification for the Alaska Peninsula bear, or an interpretation that the mainland and island populations represent the same subspecies.
The researchers also identified a common ancestor between the Alaska Peninsula bears and the Kamchatka bear (Ursus arctos beringianus). This connection is attributed to land bridges like Beringia during the ice age, which facilitated genetic exchange. The study demonstrates how paleogenomics can reveal the effects of historical events, such as ice ages, on extant species and can serve as a blueprint for similar investigations of other mammals.