Bekkevold Dorte, Glover Kevin A, Jimenez-Mena Belén, Besnier Francois, Nielsen Einar E
National Institute of Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark.
Institute of Marine Research, Bergen, Norway.
Mol Ecol. 2025 Sep;34(17):e70036. doi: 10.1111/mec.70036. Epub 2025 Jul 12.
Predicting the long-term impact of releases and introgression from non-native strains into wild populations remains an important conservation issue, particularly in fishes where stocking and aquaculture escapes have led to widespread genetic admixture between wild and cultured conspecifics. Here, we investigated the genetic response of two wild sea trout, Salmo trutta L., populations following long-term stocking programmes with non-native conspecifics. This included temporal sampling spanning 23 years and genome-wide SNP data from two neighbouring Danish rivers that from the 1970's to 1990's were heavily stocked with partially domesticated, non-local hatchery strains. To estimate wild-hatchery admixture we analysed 3656 SNPs in 195 wild-caught fish, 74 hatchery strain fish, and expanded collections temporally by analysing a subset 288 SNPs in 489 additional fish. Admixture estimates decreased from 46% to 62% input from the stocked strains to 25% seven generations after the last stocking. Introgression varied across the genome, indicative of selection for and against specific hatchery gene variants under wild conditions. For the first time in trout, strong temporal allele frequency changes were observed in a gene region harbouring the maturation gene six6 likely associated with divergent selection on age-at-maturity under hatchery versus wild conditions. The two populations showed low overlap between SNPs identified as under negative (or purifying) selection. Results point to selection against hatchery fish and partial recovery of both populations but also emphasise the role of local dynamics in shaping genetic responses to anthropogenic pressure and support the notion that introgression is likely to incur long-lasting changes to the genetic make-up of wild populations.
预测外来菌株释放和渗入野生种群的长期影响仍然是一个重要的保护问题，特别是在鱼类中，放养和水产养殖逃逸导致野生和养殖同种个体之间广泛的基因混合。在这里，我们调查了两个野生海鳟（Salmo trutta L.）种群在长期放养非本地同种个体后的遗传反应。这包括跨越23年的时间采样，以及来自丹麦两条相邻河流的全基因组SNP数据，从20世纪70年代到90年代，这两条河流大量放养了部分驯化的非本地孵化场菌株。为了估计野生与孵化场的混合情况，我们分析了195条野生捕获鱼、74条孵化场菌株鱼中的3656个SNP，并通过分析另外489条鱼中的288个SNP子集在时间上扩展了样本。混合估计从放养菌株的46%至62%的输入下降到最后一次放养七代后的25%。基因渗入在整个基因组中各不相同，表明在野生条件下对特定孵化场基因变体的选择和反选择。在鳟鱼中首次观察到，在一个包含成熟基因six6的基因区域中，等位基因频率发生了强烈的时间变化，这可能与孵化场和野生条件下成熟年龄的差异选择有关。这两个种群在被确定为负（或纯化）选择的SNP之间显示出低重叠。结果表明对孵化场鱼的选择以及两个种群的部分恢复，但也强调了局部动态在塑造对人为压力的遗传反应中的作用，并支持基因渗入可能会对野生种群的基因组成产生持久变化的观点。
