Is isolation by distance the cause of the genetic structure of the Iberian white‐throated dipper populations?

Population fragmentation in animals, by influencing dispersion between regions, may cause so‐called isolation by distance (IBD). The genetic structure of the white‐throated dipper Cinclus cinclus populations in the Iberian Peninsula was analysed using microsatellites. Birds ( n  = 226) were sampled during 2000–2012 from 12 major populations of the dipper' distribution range in the Iberian Peninsula. At the eight loci studied, 113 alleles were found. Three population groups were identified: the first comprises Sierra Cazorla and Sierra Nevada, both in the south; the second, Pyrenees and Cantabrian Mountains in the north and the third includes Central System, Galician Mountains and North Iberian System. Gene flow was high across all populations except with Sierra Cazorla and Sierra Nevada. First‐generation migration was identified between the northern and central populations, suggesting recent genetic flow across them. However, migrants from southern populations were not detected elsewhere. Genetic distances were significantly correlated with geographical distances in all populations. The genetic isolation of the southern populations may be related to the lack of suitable dipper's habitats in the lowlands of the Iberian Meseta, limiting bird dispersion and installation outside the core areas and thus the spread of their genetic characteristics. The study shows that IBD is influencing the genetic structure of Iberian dippers. Furthermore, the significant biometrical divergence identified between the southern group and the remaining populations is highly consistent with trends in genetic structure and in the geographic distance between population clusters.