Abstract
In a genetic study on brown bears (Ursus arctos) in the Cantabrian Mountains, Gregório et al. (2020) interpreted the asymmetrical gene flow they found from the eastern subpopulation towards the western one as an exodus of bears forced to flee from the eastern nucleus “with higher human disturbance and poaching”, concluding that connectivity may be operating as a means for eastern Cantabrian bears to find more suitable territories. In this reply, we maintain that the explanations of Gregorio et al. contradict the source-sink theory and we also present demographic data not considered by these authors showing that the eastern subpopulation is not declining, but persistently increasing. After reviewing the demographic and genetic studies published during the last 20 years, we conclude that the connectivity between the two subpopulations is operating as a route which allows the regular movement of males and the restoration of the gene flow across the whole Cantabrian population.
Highlights
During recent decades many populations of large carnivores have been recovering [1] and it is important to properly describe the features of the recovery processes to plan the adaptive management [2]
Gregorio et al [4] found an asymmetrical and more intense gene flow from the smaller eastern subpopulation towards the larger western subpopulation, raising the intriguing question that headed the title of their article: does the recent reconnection of both subpopulations mean a process of colonization or of an exodus of bears
We have reviewed the scientific literature to assess if human disturbance or poaching could cause an exodus from the eastern subpopulation in search for a quieter and safer habitat in the western one, as suggested by Gregorio et al [4]
Summary
During recent decades many populations of large carnivores have been recovering [1] and it is important to properly describe the features of the recovery processes to plan the adaptive management [2]. In a recent genetic study on this population of brown bears, Gregorio et al [4] confirmed that it is structured in two subpopulations (eastern and western), as previously described [3, 5,6,7,8,9]. These authors present more evidence of male mediated bidirectional gene flow and admixture between both subpopulations [3, 8]. Gregorio et al [4] found an asymmetrical and more intense gene flow from the smaller eastern subpopulation towards the larger western subpopulation, raising the intriguing question that headed the title of their article: does the recent reconnection of both subpopulations mean a process of colonization or of an exodus of bears
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