Genetic Structure and Population Affinities of Albanians: A Regional STR-Based Analysis Within the European Context.

Background/Objectives: The population genetic structure of Albania remains insufficiently characterized at both regional and broader European scales. This study investigated genetic variation within Albania and its relationship with neighboring and European populations using autosomal short tandem repeats (STRs). Methods: Sixteen autosomal STR loci were analyzed in 2000 unrelated individuals from 12 Albanian counties, grouped into Northern, Central, and Southern regions. Population structure was assessed using principal component analysis (PCA), pairwise Weir-Cockerham FST, hierarchical AMOVA, and Bayesian clustering (STRUCTURE Version 2.3.4). Population affinities were further evaluated using Nei's standard genetic distance, multidimensional scaling, and neighbor-joining analysis of European reference populations. Results: PCA revealed extensive regional overlap, with PC1 and PC2 explaining 2.64% and 2.61% of variation, respectively. Pairwise FST values were close to zero, with confidence intervals overlapping zero, while AMOVA indicated negligible regional differentiation. STRUCTURE identified K = 3 as the strongest relative solution, but ancestry coefficients showed extensive admixture without discrete regional clustering. European comparisons revealed low Nei distances (approximately 0.004-0.014), with Albania showing particularly close affinity to Greece and other Southeastern European populations. Conclusions: Albanian autosomal STR variation demonstrates high regional homogeneity and limited population substructure, while broader affinities are consistent with geographic patterns across Southeastern Europe.