Population genetic assessment of the brown bear across Northern Europe - National and transboundary perspectives and challenges

Abstract

Nowadays the brown bear (Ursus arctos) in Northern Europe is distributed from Russia to Scandinavia in the west. Refuge areas in which some brown bears survived, and immigration of bears from Russia, were assumed to be the forces behind the recovery of these populations. For some years now, large parts of Northern Europe are monitored using non-invasive genetic sampling and microsatellite markers for individual identification as well as other genetic analyses. I compare the results of the different population genetic assessments of these transboundary populations covering Norway, Sweden, Finland and parts of Northwestern Russia (1-4), plus latest updates. Population genetic structure was analyzed with Bayesian methods as well as classical population genetic indices (e.g. FST). The varying results and implications of genetic differentiation (FST, GST etc.), gene flow (private alleles, BayesAss) and population subdivision (Structure, Geneland) will be discussed. Although the majority of results support each other, a single result in itself would not be sufficient to understand the current status or be illustrative of the genetic connectivity or disconnection among different regions. At the same time, sampling scheme and geographical scale have considerable impact on the result and thus the reliability of the assessment. Overall, the results showed limitations of gene flow between the east and the west and indicated population genetic boundaries where no obvious, geographical barriers exist. Further, a mismatch between demographic and genetic connectivity was found. The multiple analyses of population differentiation and genetic variation revealed that the recovery processes of the Scandinavian brown bear population probably were different to the immigration driven recovery of the Finnish brown bear population.

References:

(1) Kopatz A, et al. (2012) Connectivity and population subdivision at the fringe of a large brown bear (Ursus arctos) population in North Western Europe. Conservation Genetics 13(3): 681-692.

(2) Schregel J, et al. (2012) Limited gene flow among brown bear populations in far Northern Europe? Genetic analysis of the east-west border population in the Pasvik Valley. Molecular Ecology 21: 3474-3488.

(3) Kopatz A, et al. (2014) Admixture and gene flow from Russia in the recovering Northern European brown bear (Ursus arctos). PLOS ONE 9(5): e97558.

(4) Schregel J, et al. (2017) Sex-specific genetic analysis indicates low correlation between demographic and genetic connectivity in the Scandinavian brown bear (Ursus arctos). PLOS ONE 12(7): e0180701.

Photo: Alexander Kopatz. Male brown bear at the Finnish-Russian border.