Centre D'Estudis Avançats de Blanes (CEAB-CSIC), Car. Acc. Cala St. Francesc 14, 17300, Blanes, Girona, Spain.
Department de Genètica, Microbiologia i Estadística and IRBio, Universitat de Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain.
Sci Rep. 2020 Jul 29;10(1):12683. doi: 10.1038/s41598-020-69160-2.
Connectivity and local adaptation are two contrasting evolutionary forces highly influencing population structure. To evaluate the impact of early-life traits and environmental conditions on genetic structuring and adaptation, we studied two sympatric fish species in the Western Mediterranean Sea: Symphodus tinca and S. ocellatus. We followed an individual-based approach and measured early-life history traits from otolith readings, gathered information on environmental variables and obtained genome-wide markers from genotyping-by-sequencing (GBS). The two species presented contrasting population structure across the same geographic gradient, with high and significant population differentiation in S. ocellatus, mostly determined by oceanographic fronts, and low differentiation and no front effect in S. tinca. Despite their different levels of genetic differentiation, we identified in both species candidate regions for local adaptation by combining outlier analysis with environmental and phenotypic association analyses. Most candidate loci were associated to temperature and productivity in S. ocellatus and to temperature and turbulence in S. tinca suggesting that different drivers may determine genomic diversity and differentiation in each species. Globally, our study highlights that individual-based approach combining genomic, environmental and phenotypic information is key to identify signals of selection and the processes mediating them.
连接性和局部适应性是两种具有鲜明对比的进化力量，对种群结构有重要影响。为了评估早期生活特征和环境条件对遗传结构和适应性的影响，我们研究了西地中海的两种共生鱼类：金头鲷和圆斑拟鳞鲀。我们采用基于个体的方法，从耳石读数中测量早期生活史特征，收集环境变量信息，并通过测序（GBS）获得全基因组标记。这两个物种在同一地理梯度上表现出截然不同的种群结构，圆斑拟鳞鲀的种群分化程度很高且具有显著意义，主要由海洋锋面决定，而金头鲷的分化程度较低且不受锋面影响。尽管它们的遗传分化程度不同，但我们通过结合外显子分析与环境和表型关联分析，在这两个物种中都发现了局部适应性的候选区域。大多数候选基因座与圆斑拟鳞鲀的温度和生产力以及金头鲷的温度和湍流有关，这表明不同的驱动因素可能决定了每个物种的基因组多样性和分化。总体而言，我们的研究强调了结合基因组、环境和表型信息的基于个体的方法是识别选择信号及其介导过程的关键。
