Section of Population Genetics and Ecology, Institute of Marine Research, Bergen, Norway.
BMC Genet. 2013 Aug 23;14:74. doi: 10.1186/1471-2156-14-74.
Many native Atlantic salmon populations have been invaded by domesticated escapees for three decades or longer. However, thus far, the cumulative level of gene-flow that has occurred from farmed to wild salmon has not been reported for any native Atlantic salmon population. The aim of the present study was to investigate temporal genetic stability in native populations, and, quantify gene-flow from farmed salmon that caused genetic changes where they were observed. This was achieved by genotyping historical and contemporary samples from 20 populations covering all of Norway with recently identified single nucleotide polymorphism markers that are collectively diagnostic for farmed and wild salmon. These analyses were combined with analysis of farmed salmon and implementation of Approximate Bayesian computation based simulations.
Five of the populations displayed statistically significant temporal genetic changes. All five of these populations became more similar to a pool of farmed fish with time, strongly suggesting introgression of farmed fish as the primary cause. The remaining 15 populations displayed weak or non-significant temporal genetic changes. Estimated introgression of farmed fish ranged from 2-47% per population using approximate Bayesian computation. Thus, some populations exhibited high degrees of farmed salmon introgression while others were more or less unaffected. The observed frequency of escapees in each population was moderately correlated with estimated introgression per population R² = 0.47 P < 0.001. Genetic isolation by distance existed within the historical and contemporary data sets, however, the among-population level of divergence decreased with time.
This is the first study to quantify cumulative introgression of farmed salmon in any native Atlantic salmon population. The estimations demonstrate that the level of introgression has been population-specific, and that the level of introgression is not solely predicted by the frequency of escapees observed in the population. However, some populations have been strongly admixed with farmed salmon, and these data provide policy makers with unique information to address this situation.
三十年来，许多本地大西洋鲑鱼种群一直受到驯化逃逸种的入侵。然而，迄今为止，尚未有任何本地大西洋鲑种群报告过来自养殖鲑鱼向野生鲑鱼的基因流动的累积水平。本研究的目的是调查本地种群的时间遗传稳定性，并量化在观察到遗传变化的地方，来自养殖鲑鱼的基因流动。这是通过使用最近确定的可用于养殖和野生鲑鱼的单核苷酸多态性标记，对涵盖挪威所有地区的 20 个种群的历史和当代样本进行基因分型来实现的。这些分析与养殖鲑鱼的分析相结合，并实施了基于近似贝叶斯计算的模拟。
五个种群显示出统计学上显著的时间遗传变化。随着时间的推移，所有这五个种群都变得与养殖鱼类群体越来越相似，这强烈表明养殖鱼类的基因渗入是主要原因。其余 15 个种群显示出较弱或不显著的时间遗传变化。使用近似贝叶斯计算，每个种群的养殖鲑鱼基因渗入估计值在 2-47%之间。因此，一些种群表现出高度的养殖鲑鱼基因渗入，而其他种群则或多或少不受影响。每个种群中逃逸种的观察频率与每个种群的估计基因渗入量呈中度相关 R²=0.47 P<0.001。历史和当代数据集内存在遗传隔离距离，但种群间的分化程度随时间而降低。
这是第一项量化任何本地大西洋鲑鱼种群中养殖鲑鱼累积基因渗入的研究。这些估计表明，基因渗入的水平是种群特异性的，并且基因渗入的水平不仅仅由种群中观察到的逃逸种频率来预测。然而，一些种群与养殖鲑鱼强烈混合，这些数据为决策者提供了独特的信息来解决这一情况。
