title: Genomewide introgressive hybridization patterns in wild Atlantic salmon influenced by inadvertent gene flow from hatchery releases.
abstract: Many salmonid fish populations are threatened by genetic homogenization, primarily due to introgressive hybridization with hatchery-reared conspecifics. By applying genomewide analysis using two molecular marker types (1986 SNPs and 17 microsatellites), we assessed the genetic impacts of inadvertent gene flow via straying from hatchery releases on wild populations of Atlantic salmon in the Gulf of Finland, Baltic Sea, over 16 years (1996-2012). Both microsatellites and SNPs revealed congruent population genetic structuring, indicating that introgression changed the genetic make-up of wild populations by increasing genetic diversity and reducing genetic divergence. However, the degree of genetic introgression varied among studied populations, being higher in the eastern part and lower in the western part of Estonia, which most likely reflects the history of past stocking activities. Using kernel smoothing and permutation testing, we detected considerable heterogeneity in introgression patterns across the genome, with a large number of regions exhibiting nonrandom introgression widely dispersed across the genome. We also observed substantial variation in nonrandom introgression patterns within populations, as the majority of genomic regions showing elevated or reduced introgression were not consistently detected among temporal samples. This suggests that recombination, selection and stochastic processes may contribute to complex nonrandom introgression patterns. Our results suggest that (i) some genomic regions in Atlantic salmon are more vulnerable to introgressive hybridization, while others show greater resistance to unidirectional gene flow; and (ii) the hybridization of previously separated populations leads to complex and dynamic nonrandom introgression patterns that most likely have functional consequences for indigenous populations.
authors: Department of Biology, University of Turku, 20014, Turku, Finland.|Kevo Subarctic Research Institute, University of Turku, 20014, Turku, Finland.
authors: M Y
authors: MY
authors: Ozerov
authors: Department of Aquaculture, Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, 51014, Tartu, Estonia.
authors: R
authors: R
authors: Gross
authors: Department of Biology, University of Turku, 20014, Turku, Finland.
authors: M
authors: M
authors: Bruneaux
authors: Department of Biology, University of Turku, 20014, Turku, Finland.|Kevo Subarctic Research Institute, University of Turku, 20014, Turku, Finland.
authors: J-P
authors: JP
authors: Vähä
authors: Department of Aquaculture, Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, 51014, Tartu, Estonia.
authors: O
authors: O
authors: Burimski
authors: Department of Aquaculture, Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, 51014, Tartu, Estonia.
authors: L
authors: L
authors: Pukk
authors: Department of Biology, University of Turku, 20014, Turku, Finland.|Department of Aquaculture, Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, 51014, Tartu, Estonia.
authors: A
authors: A
authors: Vasemägi
mesh_terms: D000818:Animals; D017756:Aquaculture; D004957:Estonia; D051456:Gene Flow; D005787:Gene Frequency; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D006824:Hybridization, Genetic; D018895:Microsatellite Repeats; D020641:Polymorphism, Single Nucleotide; D020317:Salmo salar / Q000235:genetics*; D017422:Sequence Analysis, DNA
keywords: Atlantic salmon; genetic homogenization; genomewide; hatchery releases; introgressive hybridization; straying