Paleobiogeography of two Iberian endemic cyprinid fishes (Chondrostoma arcasii-Chondrostoma macrolepidotus) inferred from mitochondrial DNA sequence data.

We tested different hypotheses related to the origin and evolution of the endemic Iberian fishes Chondrostoma arcasii and Chondrostoma macrolepidotus from northern and central regions of the Iberian Peninsula. We evaluated the monophyly of the populations within each species and sought to determine if diversification of the populations coincided in time with the formation of the Iberian drainages dating back to the upper Pliocene (2.5-1.8 million years ago). A molecular phylogenetic analysis of the mitochondrial cytochrome b gene showed that the different populations of the northern Iberian Peninsula are clustered into five phylogroups and do not fit into the dichotomy C. arcasii-C. macrolepidotus. We propose that species differentiation occurred prior to the upper Pliocene formation of the present hydrographic basins and that endorheic basins, a system of inland lakes found in Spain during the Mio-Pliocene, played an important role in this diversification and differentiation process.