Genetic Screening of Distribution Pattern of Roaches Rutilus rutilus and R. lacustris (Cyprinidae) in Broad Range of Secondary Contact (Volga Basin)

We investigated the distribution of mitochondrial lineages of two species—the common roach Rutilus rutilus and Ponto-Caspian roach R. lacustris—in the broadest zone of their secondary contact, the Volga basin. For the purpose of species identification, we applied the approach of multiplex PCR based on species-specific divergences in sequences of the first subunit of cytochrome oxidase (COI) of mtDNA. A total of 1120 samples from 82 localities are analyzed. The distribution of certain mitochondrial lineages and their sympatric co-occurrence clarified for the Volga basin. Our study shows that R. rutilus is significantly predominant in the Upper Volga, while the Middle and Lower Volga is dominated by R. lacustris. The various hypotheses of formation of the broad spatial pattern of secondary contact are discussed.