title: Migration and isolation during the turbulent Ponto-Caspian Pleistocene create high diversity in the crustacean Paramysis lacustris.
abstract: The Ponto-Caspian brackish-water fauna inhabits estuaries and rivers of the Black, Azov and Caspian seas and is fragmented by higher salinity waters and a major interbasin watershed. The fauna is known for the high levels of endemism, complex zoogeographic histories, and as a recent source of successful invasive species. It remains debated whether the Black and Azov Sea brackish-water populations survived unfavourable Pleistocene conditions in multiple separate refugia or whether the two seas were (repeatedly) recolonized from the Caspian. Using microsatellite and mtDNA markers, we demonstrate deep among- and within-basin subdivisions in a widespread Ponto-Caspian mysid crustacean Paramysis lacustris. Five genetic clusters were identified, but their relationships did not reflect the geography of the region. The Azov cluster was the most distinct (4-5% COI divergence), despite its geographic position in the corridor between Black and Caspian seas, and may represent a new species. In the northern Black Sea area, the Dnieper cluster was closer to the Caspian cluster than to the neighbouring Danube-Dniester-Bug populations, suggesting separate colonizations of the Black Sea. Overall, the data implied a predominant gene flow from the east to the Black Sea and highlight the importance of Caspian Sea transgressions in facilitating dispersal. Yet, the presence of distinct lineages in the Black Sea points to the persistence of isolated refugial populations that have gained diagnostic differences under presumably high mutation rates and large population sizes. The unfavourable Pleistocene periods in the Black Sea therefore appear to have promoted diversification of the brackish-water lineages, rather than extirpated them.
authors.affiliation: Nature Research Centre, Akademijos 2, Vilnius, LT-08412, Lithuania.|Department of Environmental Sciences, University of Helsinki, POB 65, Helsinki, FIN-00014, Finland.
authors.forename: Asta
authors.initials: A
authors.lastname: Audzijonyte
authors.affiliation: Nature Research Centre, Akademijos 2, Vilnius, LT-08412, Lithuania.
authors.forename: Laima
authors.initials: L
authors.lastname: Baltrūnaitė
authors.affiliation: Finnish Museum of Natural History, University of Helsinki, POB 17, Helsinki, FIN-00014, Finland.
authors.forename: Risto
authors.initials: R
authors.lastname: Väinölä
authors.affiliation: Nature Research Centre, Akademijos 2, Vilnius, LT-08412, Lithuania.|Department of Zoology, Vilnius University, M. K. Čiurlionio 21/27, Vilnius, LT-03101, Lithuania.
authors.forename: Kęstutis
authors.initials: K
authors.lastname: Arbačiauskas
mesh_terms: D000818:Animals; D005075:Biological Evolution; D059038:Black Sea; D003445:Crustacea / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D051456:Gene Flow; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: COI; Mysida; Pleistocene; gene flow; phylogeography