Probable direction of the postglacial colonization of rivers on northern slopes of the Carpathian Ridge by Barbus carpathicus (Teleostei: Cyprinidae) evidenced by cline of genetic variation

A cline in microsatellite diversity appeared among populations of Barbus carpathicus in four adjacent river basins on the northern slopes of the Carpathian Ridge, with western populations more variable than eastern ones ( H _S equals 0·45, 0·32, 0·23 and 0·13, respectively). Overall genetic variation was low, likely reflecting population bottlenecks during postglacial expansions through the Danube–Vistula watershed and eastward into Carpathian tributaries of the Vistula River. Genetic similarities between populations in the westernmost tributary of the Dniester (Strwiąż River) and those in the adjacent Vistula tributary (San River) suggest that at least the western part of the Dniester basin was colonized from the Vistula River system.