A recent study published in the journal Molecular Biology and Evolution shows that the Appenino brown bear population, which lives in central Italy and has been close to human settlements for a long time, has significantly different characteristics from other brown bears in size and temperament: they are overall smaller and less aggressive. Behind this, clear selection pressure from human activities and genetic adaptation signals can be seen. The scientific research team pointed out that the evolutionary history of this small isolated population shows that continued human presence will not only increase the risk of species extinction, but may also quietly promote the evolution of traits that alleviate human-bear conflicts.
The research object is the Appenino brown bear (Ursus arctos marsicanus), an extremely rare and geographically restricted brown bear population that is only found in the mountains of central Italy and has coexisted closely with local human society for hundreds of years. Previous research has inferred that this bear group diverged from other European brown bears about 2,000 to 3,000 years ago and has been almost completely isolated since Roman times. Andrea Benazzo, the first author of the study, pointed out that forest clearing, agricultural expansion and increasing population density are likely to be the main reasons for the population's decline and spatial isolation.
Today, Appenino brown bears look and behave markedly different from other brown bears in Europe, North America, and Asia: they are smaller on average, have relatively unique head and facial features, and display less aggression. The core question of this new study is to try to clarify how recent human pressure has shaped the evolutionary trajectory of this endangered small population, and whether there is an identifiable genetic basis behind this "moderating".
The scientific research team first established a high-quality chromosome-level reference genome of the Appennino brown bear and sequenced the whole genome of multiple individuals. They then compared these data with the large European brown bear population from Slovakia and the existing American brown bear genome data. The analysis results showed that the genome diversity of the Appennino brown bears was significantly reduced and the level of inbreeding was higher, which is consistent with its long-term small population size and geographical isolation. More importantly, the researchers found selection signals related to "reduced aggression" at some genetic loci, suggesting that behavioral traits have undergone targeted evolution in this small population.
Giulia Fabbri, co-author of the paper, pointed out that humans' long-term tendency to hunt more aggressive individuals in the past may have strengthened the genetic variants associated with docile behavior, causing the entire group to gradually tilt toward "low conflict" behavior. On the one hand, this selection process exacerbates population decline and genome erosion, increasing the risk of extinction. On the other hand, it inadvertently promotes a decrease in the intensity of human-bear conflicts, making these animals better able to survive in environments with high human interference. Giorgio Bertorelle, a member of the research team, emphasized that human-wildlife interactions often pose a threat to species survival, but may also promote the evolution of traits that reduce conflicts. Therefore, for such small populations that have been deeply negatively affected by human activities, when implementing conservation measures such as restocking, their hard-won genetic variation with potential adaptive value should not be easily diluted.
The study is titled "Coexisting With Humans: Genomic and Behavioral Consequences in a Small and Isolated Bear Population". The author team comes from the University of Ferrara in Italy and other institutions. The project received financial support from the MIUR PRIN 2017 project of the Italian Ministry of Universities and Research, the Young Researchers Program, and the European Union's "NextGenerationEU" National Biodiversity Future Center. The research results also provide important reference for the conservation of other wild animals living in high human intervention environments.
Compiled from /ScitechDaily