A study in the journal Molecular Biology and Evolution examines the Apennine brown bear, Ursus arctos marsicanus, a distinct population that occurs only in central Italy and has long lived close to rural communities. Previous work suggests these bears split from other European brown bears 2000 to 3000 years ago and have remained isolated since Roman times, a pattern researchers link to forest clearance, agriculture, and rising human population density in the region.
Today Apennine brown bears differ in several visible and behavioral traits compared with European, North American, and Asian brown bears. They are smaller, have distinctive head and facial characteristics, and show less aggressive behavior than other brown bear populations.
To investigate how recent human-driven environmental pressures shaped this population, the team produced a high-quality chromosome-level reference genome for the Apennine brown bear and sequenced whole genomes from multiple individuals. They compared these data with genomes from a larger European brown bear population in Slovakia and previously published genomes from American brown bears to identify genetic and evolutionary differences.
The researchers analyzed genomic diversity and searched for signatures of adaptation specific to the Italian population. As expected for a small, isolated group, Apennine brown bears showed reduced genomic diversity and higher inbreeding relative to other brown bears.
More notably, the team identified selective signals in genes associated with reduced aggressiveness, pointing to evolutionary changes that track behavior. "More interestingly, however, we showed that Apennine brown bears also possess selective signatures at genes associated with reduced aggressiveness."
The authors interpret these patterns as evidence that selection on behavior-related genetic variants, probably influenced by the human removal of more aggressive individuals, helped produce a less aggressive bear population over time. This process illustrates how human encroachment into natural habitats can both drive demographic declines and genomic erosion, increasing extinction risk while also favoring traits that reduce direct conflict between humans and wildlife.
"The general implications of our findings are clear," concluded Giorgio Bertorelle, another researcher involved in the study, "human-wildlife interactions are often dangerous for the survival of a species, but may also favor the evolution of traits that reduce conflict. This means that even populations that have been heavily and negatively affected by human activities may harbor genetic variants that should not be diluted, for example, by restocking."
Research Report:Coexisting with humans: genomic and behavioural consequences in a small and isolated bear population
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