Genetic differentiation and asymmetric gene flow among Carpathian brown bear (Ursus arctos) populations—Implications for conservation of transboundary populations

Abstract

The abundance and distribution of large carnivores in Europe have been historically reduced. Their recovery requires multilevel coordination, especially regarding transboundary populations. Here, we apply nuclear and mitochondrial genetic markers to test for admixture level and its impact on population genetic structure of contemporary brown bears (Ursus arctos) from the Eastern, Southern, and Western Carpathians. Carpathian Mountains (Europe). Nearly 400 noninvasive brown bear DNA samples from the Western (Poland) and Eastern Carpathians (Bieszczady Mountains in Poland, Slovakia, Ukraine) were collected. Together with DNA isolates from Slovakia and Romania, they were analyzed using the set of eight microsatellite loci and two mtDNA regions (control region and cytochrome b). A set of 113 individuals with complete genotypes was used to investigate genetic differentiation across national boundaries, genetic structuring within and between populations, and movement between populations. Transboundary brown bear subpopulations (Slovakia and Poland) did not show significant internal genetic structure, and thus were treated as cohesive units. All brown bears from the Western Carpathians carried mitochondrial haplotypes from the Eastern lineage, while the Western lineage prevailed in the brown bears from the Bieszczady Mountains. Despite similar levels of microsatellite variability, we documented significant differentiation among the studied populations for nuclear markers and mtDNA. We also detected male‐biased and asymmetrical movement into the Bieszczady Mountains population from the Western Carpathians. Our findings suggest initial colonization of the Western Carpathians by brown bears possessing mtDNA from the Eastern lineage. Genetic structuring among populations at microsatellite loci could be a result of human‐mediated alterations. Detected asymmetric gene flow suggests ongoing expansion from more abundant populations into the Bieszczady Mountains and thus supports a metapopulation model. The knowledge concerning this complex pattern can be implemented in a joint Carpathian brown bear management plan that should allow population mixing by dispersing males.

Not exodus, but population increase and gene flow restoration in Cantabrian brown bear (Ursus arctos) subpopulations. Comment on Gregório et al. 2020

“…Unlike Gregório et al [ 4 ], all previous studies have found a predominant flow of males from the western to the eastern subpopulation [ 3 , 5 , 8 ], an asymmetric gene flow similar to that found in other populations [ 47 ]. The differences in the direction of the gene flow detected in different studies may be related to the limited number of samples collected by these studies or because change in dispersal magnitude and direction is an inherent property of a dynamic recovering metapopulation [ 48 ].…”

Multisource noninvasive genetics of brown bears (Ursus arctos) in Greece reveals a highly structured population and a new matrilineal contact zone in southern Europe

“…This unexpected result marks the Hellenic Peninsula as the southernmost region the Eastern lineage has been detected and draws a new southernmost secondary contact zone between Eastern and Western mtDNA lineages in Europe (Figure 4). One possible explanation is that Eastern Davison et al, 2011;Bray et al, 2013;Çilingir et al, 2016;Matosiuk et al, 2019). Clades 1a and 1b belong to the Western mtDNA lineage and 3a1 to the Eastern mtDNA lineage.…”

Noninvasive Genetics Knowledge from the Brown Bear Populations to Assist Biodiversity Conservation

“…The nNGS proves the need to study transboundary bear populations to provide interesting outcomes [64,71,79,84,153,154]. Three individuals' DNA from FYR Macedonia was also detected in Greece, and this demonstrates the presence of a single interconnected population [84].…”