Survival and divergence in a small group: The extraordinary genomic history of the endangered Apennine brown bear stragglers.

摘要: About 100 km east of Rome, in the central Apennine Mountains, a critically endangered population ∼50 brown bears live complete isolation. Mating outside this is prevented by several bear-free territories. We exploited natural experiment to better understand gene and genomic consequences surviving at extremely small size. found that bear populations Europe lost connectivity since Neolithic times, when farming communities expanded forest burning was used for land clearance. In Italy, resulted 40-fold decline. The overall impact decline included loss variation mitochondrial genome along long stretches nuclear genome. Several private deleterious amino acid changes were fixed random drift; predicted effects include energy deficit, muscle weakness, anomalies cranial skeletal development, reduced aggressiveness. Despite extreme diversity, genomes show nonrandom peaks high variation, possibly maintained balancing selection, regions significantly enriched genes associated with immune olfactory systems. Challenging paradigm increased extinction risk populations, we suggest fixation alleles (i) can be an important driver divergence isolation, (ii) tolerated selection prevents genes, (iii) followed or results directly favorable behavioral changes.