Genetic Structure of Bluefin Tuna in the Mediterranean Sea Correlates with Environmental Variables

BackgroundAtlantic Bluefin Tuna (ABFT) shows complex demography and ecological variation in the Mediterranean Sea. Genetic surveys have detected significant, although weak, signals of population structuring; catch series analyses and tagging programs identified complex ABFT spatial dynamics and migration patterns. Here, we tested the hypothesis that the genetic structure of the ABFT in the Mediterranean is correlated with mean surface temperature and salinity.MethodologyWe used six samples collected from Western and Central Mediterranean integrated with a new sample collected from the recently identified easternmost reproductive area of Levantine Sea. To assess population structure in the Mediterranean we used a multidisciplinary framework combining classical population genetics, spatial and Bayesian clustering methods and a multivariate approach based on factor analysis.ConclusionsFST analysis and Bayesian clustering methods detected several subpopulations in the Mediterranean, a result also supported by multivariate analyses. In addition, we identified significant correlations of genetic diversity with mean salinity and surface temperature values revealing that ABFT is genetically structured along two environmental gradients. These results suggest that a preference for some spawning habitat conditions could contribute to shape ABFT genetic structuring in the Mediterranean. However, further studies should be performed to assess to what extent ABFT spawning behaviour in the Mediterranean Sea can be affected by environmental variation.背景 大西洋蓝鳍金枪鱼（Atlantic Bluefin Tuna, ABFT）在地中海海域呈现出复杂的种群动态与生态变异。遗传调查已检测到虽微弱但显著的种群结构信号；渔获序列分析与标记项目揭示了ABFT复杂的空间动态与洄游模式。本研究检验了地中海ABFT的遗传结构与表层平均温度、盐度存在相关性这一假说。 方法 我们采用了采自地中海西部与中部的6份样本，并补充了一份采自新近发现的黎凡特海最东端产卵场的新样本。为评估地中海地区的种群结构，我们采用了融合经典种群遗传学、空间聚类与贝叶斯聚类方法，以及基于因子分析的多变量分析的多学科研究框架。 结论 FST分析与贝叶斯聚类方法在地中海海域检测到多个亚种群，该结果也得到多变量分析的支持。此外，我们发现遗传多样性与平均盐度、表层温度存在显著相关性，表明ABFT的遗传结构沿两条环境梯度分布。上述结果暗示，对特定产卵栖息地条件的偏好可能塑造了地中海ABFT的遗传结构。不过，仍需开展进一步研究以明确地中海海域ABFT的产卵行为在多大程度上会受到环境变化的影响。