Data from: Temporal genetic stability and high effective population size despite fisheries-induced life-history trait evolution in the North Sea sole.

Heavy fishing and other anthropogenic influences can have profound impact on a species’ resilience to harvesting. Besides the decrease of the census and effective population size, strong declines in mature adults and recruiting individuals may lead to almost irreversible genetic changes in life-history traits. Here, we investigated the evolution of genetic diversity and effective population size in the heavily exploited sole (Solea solea), through the analysis of historical DNA from a collection of 1379 sole (Solea solea) otoliths dating back from 1957. Despite documented shifts in life-history traits, neutral genetic diversity inferred from 11 microsatellite markers showed a remarkable stability over a period of 50 years of heavy fishing. Using simulations and corrections for fisheries induced demographic variation, both point and temporal estimates of effective population size (Ne) were always higher than 1000, suggesting that despite the severe census size decrease over a 50 year period of harvesting, genetic drift is probably not strong enough to significantly decrease the neutral diversity of this species in the North Sea. However the ratio of effective population size to the census size (Ne/Nc) was very small (10-5), suggesting that overall only few adults contribute to the next generation. The high Ne level together with the low Ne/Nc ratio is most likely caused by a combination of an equalized reproductive output of younger cohorts, a decrease in generation time and a large variance in reproductive success typical for marine species. Because strong evolutionary changes in age and size at first maturation have been observed for sole, changes in adaptive genetic variation should be further monitored to detect the evolutionary consequences of human-induced selection.

高强度捕捞及其他人为活动，会对物种应对捕捞胁迫的恢复能力产生深远影响。除普查种群数量与有效种群大小（effective population size）下降之外，成熟个体及补充群体个体的大幅减少，可能会导致生活史特征（life-history traits）出现几乎不可逆的遗传改变。本研究通过对1957年以来采集的1379枚欧洲鳎（Solea solea）耳石（otoliths）中的历史DNA（historical DNA）进行分析，探究了高强度捕捞压力下该物种的遗传多样性及有效种群大小的演化规律。尽管已有研究记录了该物种生活史特征的改变，但通过11个微卫星标记（microsatellite markers）推断得到的中性遗传多样性（neutral genetic diversity），在长达50年的高强度捕捞期间仍表现出显著的稳定性。本研究通过模拟分析及对捕捞引发的种群动态变化进行校正，结果显示有效种群大小（effective population size, Ne）的点估计与时间序列估计值均始终高于1000，这表明尽管在50年的捕捞期中普查种群数量大幅下降，但遗传漂变（genetic drift）的作用强度或许不足以显著降低北海海域该物种的中性遗传多样性。然而，有效种群大小与普查种群数量的比值（Ne/Nc）极低，仅为10^-5，这意味着整体而言仅有极少数成熟个体能够为下一代贡献基因。较高的有效种群大小水平与极低的Ne/Nc比值，大概率是由以下多种因素共同作用所致：较年轻同龄群的繁殖产出趋于均等、世代时间缩短，以及海洋物种典型的繁殖成功率（reproductive success）存在较大变异。鉴于已有研究观测到欧洲鳎的初次性成熟年龄与体型发生了显著的演化改变，因此需进一步监测适应性遗传变异（adaptive genetic variation）的变化，以揭示人为诱导选择所带来的演化后果。