Genome-wide insights into genetic diversity of endemic and non-endemic Ixodes ricinus populations

Ixodes ricinus, a major vector of tick-borne pathogens in Europe, exhibits considerable geographic variation in genetic structure and vector competence. This study investigates genome-wide polymorphism and population structure in I. ricinus populations from Türkiye -where tick-borne encephalitis (TBE) is not endemic-compared to populations from Germany and Algeria, for which genomic data are publicly available. Whole-genome sequencing was performed on 15 individuals from four geographically distinct Turkish populations and evaluated with German and Algerian samples available in GenBank. Principal component analysis (PCA) and ADMIXTURE clustering revealed clear genetic separation between Turkish and German populations. Genomic diversity scans identified 37 highly differentiated genomic regions, several of which contained genes associated with detoxification, lipid metabolism, chemosensory processes, and ion transport-functions relevant to vectorial capacity and local adaptation. Gene Ontology enrichment analyses supported these findings, highlighting overrepresentation of carotene and terpene metabolism pathways. Notably, Turkish populations exhibited more admixture and heterogeneity than the genetically homogeneous German population. These results highlight region-specific genomic differentiation in I. ricinus, which may influence ecological interactions and vector-associated traits.