Phylogeography of the barbel (Barbus barbus) assessed by mitochondrial DNAvariation

Using the phylogeographic framework, we assessed the DNA sequence variation at the mitochondrial cytochrome b gene across the distribution range of th e barbel Barbus barbus, a widely distributed European cyprinid. Reciprocal monophyly of non-Mediterranean European and Balkan/Anatolian populations is taken as evidence for a long-term barrier to gene flow, and interpreted as a consequence of survival of the species in two separate refugia during se veral later glacial cycles. Lack of profound genealogical divergence across Europe from western France to the northwestern Black Sea basin is consiste nt with recent colonization of this area from a single glacial refuge, whic h was probably located in the Danube River basin. This may have occurred in two steps: into the Western European river basins during the last intergla cial, and throughout the Central European river basins after the last glaci al. The populations from the Balkans and Anatolia apparently did not contri bute mitochondrial DNA to the post-Pleistocene colonization of non-Mediterr anean Europe. Lack of detectable variation within the Balkans/Anatolia is a ttributed mainly to recent expansion throughout these regions, facilitated by the freshwater conditions and seashore regression in the Black Sea durin g the Late Pleistocene and Early Holocene.