Wolf samples were collected from 31 countries across Eurasia, with a particular focus on Europe. A dataset of 1,090 genomes (817 newly sequenced) was used for population genomic analysis. To account for differences in sequencing quality between samples, the genomes imputed using a reference dataset of 1,519 canids. After quality control, a final dataset of 667 individuals and 29 million high-quality genetic variants was used for downstream analysis.
Population structure analysis revealed 15 genetically distinct wolf populations across Eurasia (12 in Europe), refining the 9 groups defined by the LCIE and currently used for conservation management. The Italian wolf population was found to have expanded northwards beyond the Alps into Germany, and fine-scale genetic structure was identified within the Baltic and Fennoscandian regions. Captive wolves from Finland and Norway had a distinct genetic makeup compared to wild individuals, potentially preserving genetic diversity that has been lost from the wild.
Wolves from northern Europe (Fennoscandia and the Northern Baltics) showed genetic sharing with Asian wolves, indicating gene flow from the east consistent with the known recolonization of Finland and Karelian Russia in the 1950s, followed by recolonization of the Scandinavian Peninsula in the 1970s by a single breeding pair from Finland. In contrast, wolves in southern Europe, particularly in Italy and Iberia, showed an increased genetic similarity to European wolves from earlier in the Holocene period, indicating that long-term isolation on their respective peninsulas had preserved ancient ancestry.
Dog ancestry in wolf genomes was highly region-specific. Some populations showed no significant dog ancestry despite recent population bottlenecks, likely because hybrids are actively removed. Wolves in Ukraine and Italy showed high levels of dog introgression (40% and 44% of individuals respectively), with individual wolves in Ukraine carrying up to 20% dog ancestry. This indicates pervasive and ongoing dog admixture in these regions requiring close monitoring.
Most wolf populations in Europe have declined in effective population size over the past 200 years. Conservation biologists typically use a minimum effective population size of 500 individuals as a benchmark for long-term genetic viability. Although most populations have grown since the 1970s, many still fall short of this threshold, showing that European wolves remain genetically fragile despite large census numbers.
High levels of genetic load and inbreeding were found in Scandinavian wolves as a result of a recent founder bottleneck. Wolves in the Italian and Iberian peninsulas also show high inbreeding but reduced genetic load due to the gradual purging of deleterious variants over many generations. However, their low diversity limits adaptive potential, and while wolves are expanding out of Italy, there is currently no evidence of gene flow back into either peninsula.
Preliminary analysis of historical museum specimens, mostly from Karelian Russia and Fennoscandia, has also revealed complete population turnovers in both regions, consistent with known local extinctions and later recolonization, with genomic evidence of increased inbreeding at the time of each collapse. The modern Scandinavian population carries no genetic trace of the historic population it replaced and is instead most similar to captive wolves from Sweden and Finland.
