title: Genetic differentiation of brackish water populations of cod Gadus morhua in the southern Baltic, inferred from genotyping using SNP-arrays.
abstract: The Baltic is a semi-enclosed sea characterised by decreasing salinity in the eastern and northern direction with only the deeper parts of the southern Baltic suitable as spawning grounds for marine species like cod. Baltic cod exhibits various adaptations to brackish water conditions, yet the inflow of salty North Sea water near the bottom remains an influence on the spawning success of the Baltic cod. The eastern Baltic population has been very weakly studied in comparison with the western population. The aim of this study is to demonstrate for the first time genetic differentiation by the use of a large number of SNPs between eastern and western Baltic populations existing in differentiated salinity conditions. Two cod samples were collected from the Bay of Gdańsk, Poland and one from the Kiel Bight, Germany. Samples were genotyped using a cod derived SNP-array (Illumina) with 10 913 SNPs. A selection of diagnostic SNPs was performed. A set of 7944 validated SNPs were analysed to assess the differentiation of three samples of cod. Results indicated a clear distinctness of the Kiel Bight from the populations of the eastern Baltic. FST comparison between both eastern samples was non-significant. Clustering analysis, principal coordinates analysis and assignment test clearly indicated that the eastern samples should be considered as one subpopulation, well differentiated from the western subpopulation. With the SNP approach, no differentiation between groups containing 'healthy' and 'non-healthy' cod individuals was observed.
authors.affiliation: Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Poćwierz-Kotus
authors.affiliation: Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Kijewska
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Research Unit: Evolutionary Ecology of Marine Fish, 24105 Kiel, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Petereit
authors.affiliation: Department of Migratory Fishes in Gdansk, Inland Fisheries Institute, Olsztyn, Poland.
authors.forename: R
authors.initials: R
authors.lastname: Bernaś
authors.affiliation: Department of Fish Systematics, Faculty of Food Sciences and Fisheries, West Pomeranian University of Technology, K. Krolewicza 4, 71-550 Szczecin, Poland.
authors.forename: B
authors.initials: B
authors.lastname: Więcaszek
authors.affiliation: Centre for Integrative Genetics (CIGENE), Norwegian University of Life Sciences, Ås, Norway.
authors.forename: M
authors.initials: M
authors.lastname: Arnyasi
authors.affiliation: Centre for Integrative Genetics (CIGENE), Norwegian University of Life Sciences, Ås, Norway.
authors.forename: S
authors.initials: S
authors.lastname: Lien
authors.affiliation: Centre for Integrative Genetics (CIGENE), Norwegian University of Life Sciences, Ås, Norway.
authors.forename: M P
authors.initials: MP
authors.lastname: Kent
authors.affiliation: Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland.
authors.forename: R
authors.initials: R
authors.lastname: Wenne
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000704:Analysis of Variance; D000818:Animals; D016000:Cluster Analysis; D048389:Gadus morhua / Q000235:genetics*; D005787:Gene Frequency; D014644:Genetic Variation; D060005:Genotyping Techniques; D005858:Germany; D009792:Oceans and Seas; D011044:Poland; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D000068357:Saline Waters
keywords: Baltic Sea; Cod; Population genomics; SNP markers; Salinity