Imprints from genetic drift and mutation imply relative divergence times across marine transition zones in a pan-European small pelagic fish (Sprattus sprattus)

Geographic distributions of most temperate marine fishes are affected by post-glacial recolonisation events which have left complex genetic imprints on populations of marine species. This study investigated population structure and demographic history of European sprat (Sprattus sprattus L.) by combining inference from both mtDNA and microsatellite genetic markers throughout the species distribution. We compared effects from genetic drift and mutation for both genetic markers in shaping genetic differentiation across four transition zones. Microsatellite markers revealed significant isolation by distance and a complex population structure across the species' distribution (overall θST = 0.038, p < 0.01). Across transition zones markers indicated larger effects of genetic drift over mutations in the northern distribution of sprat contrasting a stronger relative impact of mutation in the species southern distribution in the Mediterranean region. These results were interpreted to reflect...