Quaternary geomorphological and climatic changes associated with the diversification of Iberian freshwater fishes: The case of the genus Cobitis (Cypriniformes, Cobitidae).

We studied the population genetic structure of Cobitis vettonica , an endangered freshwater fish species endemic to the Iberian Peninsula, in order to propose a biogeographic model of the responses of species to the multiple changes that occurred in the Iberian hydrological system during the Quaternary period. We also deciphered the relationship of C . vettonica with its sister species C . paludica , particularly in sympatric areas, and provide genetic information for conservation purposes. To achieve this goal, we analyzed both mitochondrial and nuclear data (the cytochrome b and the nuclear recombination activating 1 genes) and a battery of single-nucleotide polymorphisms (SNPs) of 248 individuals of C . vettonica or C . paludica from 38 localities, including some sympatric ones, covering the entire distribution area of C . vettonica . We highlight the important role played by the hydrogeomorphological processes and climatic changes that occurred in the Iberian Peninsula during the Quaternary on both the population structure of C . vettonica and its relationship with its sister species C . paludica . Our results support the genetic introgression of populations at the eastern limit of the distribution of C . vettonica . Furthermore, we postulate genetic introgression in sympatric areas. Finally, we propose the establishment or expansion of four Operational Conservation Units (OCUs) for C . vettonica , and highlight the threat faced by its populations due to the low level of genetic diversity detected for some of its populations and genetic introgression with C . paludica , which could eventually displace C . vettonica , resulting in a loss of diversity in this species.