Population genomics of the southern Caspian Sea Vobla Rutilus lacustris

The genus Rutilus is widespread in the western and central Palearctic region. In the Caspian Sea, the taxonomic status of different populations of Rutilus lacustris has been debated due to different sub-specific names attributed to each population. We genotyped 7,984 single nucleotide polymorphisms and sequenced the mitochondrial cytochrome C oxidase subunit I gene of 37 R. lacustris and Rutilus frisii from the southeast and southwest Caspian Sea and the Aras River in the Kura River drainage. We analysed data using clustering, Bayes factor delimitation, introgression, assessment of migration rate, and phylogenetic analyses. The results showed that the southeast and southwest Caspian Sea populations of R. lacustris were closely related, but highly differentiated from R. lacustris in the Aras River. The Bayes factor delimitation test supported the existence of three populations of R. lacustris in the studied area. Three hybrid individuals with mtDNA from Abramis brama or R. frisii and nuclear DNA from R. lacustris were detected. To protect R. lacustris in the southern Caspian Sea, we propose that the Aras River and sea-run R. lacustris be treated as two separate conservation units and the southern Caspian Sea R. lacustris populations should be viewed as two potentially separate management units.