Differences in levels of heterozygosity in populations of the common gudgeon (Gobio gobio, Cyprinidae) among adjacent drainages in Central Europe: An effect of postglacial range dynamics?

Abstract

Twenty-nine allozyme loci analyzed in 295 common gudgeons (Gobio gobio) from the Rhine, the upper Danube and the Elbe river systems revealed variability measures of P = 0.590, He = 0.066, and GST = 0.1415. Gene flow was estimated at Nem = 1.88 over 223 river km in the Danube basin, and at Nem = 1.96 over 300 river km in the Rhine system. Isolation-by-distance was not observed. Danubian gudgeons proved significantly more heterozygous (He = 0.106) than those from the Rhine (He = 0.057) or the Elbe drainages (He = 0.029). Nine polymorphic enzymes contributed to this difference, which probably indicates dispersal bottlenecking of the postglacial immigrants into the Atlantic drainages of the study area. Refugial bottlenecking of gudgeons from Atlantic drainages in a Pleistocene refuge located in oceanic northwest Europe also seems possible. Slightly deeper generic lineages in the Danube (GST = 0.0859) than in the Rhine (GST = 0.0793) agree with this explanation, as does the greater mean genetic distance among pairs of population samples from the Danube (D = 0.0138) than from the Rhine (D = 0.0054). A genetic distance of D = 0.0085 separated Rhenish and Danubian gudgeons.