Heterogeneous colonization pattern of European Cyprinids, as highlighted by the dace complex (Teleostei: Cyprinidae).

The dace (Leuciscus leuciscus), with a very large geographic distribution all over Europe, represents an interesting species model for studies of the global mechanisms underlying aquatic system biodiversity. To assess the congruence with the past colonization process hypothesis of the freshwater fauna in Western Europe, we investigated the evolutionary history of this species, by integrating morphological variation (eight meristic characters), mitochondrial (cytochrome b, 16S rDNA and control region, over a total of 2169 bp) and nuclear (12 allozymes loci) phylogenetic relationships, and investigating population dynamics via expansion, migration, bottleneck, and divergence time analyses. We carried out nested clade phylogeographic analysis for a total of 663 specimens from 31 populations taken from all over the distribution area. Unlike previous studies, we found that L. leuciscus is currently constituted by five lineages belonging to two clades (yielding 6.3% of pairwise divergence). The relationships between these lineages were accounted for by complex biogeographical patterns due to Pliocene and Pleistocene paleoclimatic events, validating the identification of new glacial refuges for freshwater fish in Western Europe. Finally, we demonstrated hybridization between L. leuciscus and Leuciscus idus.