Centre for Ecology, Evolution and Behavior, School of Biological Sciences, Royal Holloway University of London, Egham, United Kingdom ; Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, South Africa.
Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, South Africa.
PLoS One. 2014 Feb 20;9(2):e87907. doi: 10.1371/journal.pone.0087907. eCollection 2014.
Contemporary patterns of genetic diversity and population connectivity within species can be influenced by both historical and contemporary barriers to gene flow. In the marine environment, present day oceanographic features such as currents, fronts and upwelling systems can influence dispersal of eggs/larvae and/juveniles/adults, shaping population substructuring. The Benguela Current system in the southeastern Atlantic is one of the oldest upwelling systems in the world, and provides a unique opportunity to investigate the relative influence of contemporary and historical mechanisms shaping the evolutionary history of warm-temperate fish species. Using the genetic variation in the mitochondrial DNA Control Region and eight nuclear microsatellite DNA loci, we identified the presence of two highly divergent populations in a vagile and warm-temperate fish species, Atractoscion aequidens, across the Benguela region. The geographical distributions of the two populations, on either side of the perennial upwelling cell, suggest a strong correlation between the oceanographic features of the system and the breakdown of gene flow within this species. Genetic divergence (mtDNA φ ST = 0.902, microsatellite F ST = 0.055: probability of genetic homogeneity for either marker = p<0.001), absence of migrants (less than 1% per generation) between populations and coalescent estimates of time since most recent common ancestor suggest that the establishment of the main oceanographic features of the system (2 million years ago), particularly the strengthening and position of the perennial upwelling cell, is the most likely mechanism behind the observed isolation. Concordance between mitochondrial and nuclear genetic markers indicates that isolation and divergence of the northern and southern Benguela populations of A. aequidens occurred deep in the past and has continued to the present day. These findings suggest that the Benguela Current system may constitute an ancient and impermeable barrier to gene flow for warm-temperate fish species.
当代物种内的遗传多样性和种群连通性模式可能受到历史和当代基因流动障碍的影响。在海洋环境中，当前的海洋特征，如洋流、锋面和上升流系统，会影响卵/幼虫和/或幼鱼/成鱼的扩散，从而影响种群的亚结构。东南大西洋的本格拉洋流系统是世界上最古老的上升流系统之一，为研究塑造暖温鱼类进化历史的当代和历史机制的相对影响提供了独特的机会。本研究利用线粒体 DNA 控制区和 8 个核微卫星 DNA 位点的遗传变异，在本格拉地区发现了一种洄游性暖温鱼类阿氏前鳍鲹（Atractoscion aequidens）中存在两个高度分化的种群。这两个种群的地理分布位于常年上升流细胞的两侧，表明该系统的海洋特征与该物种内部基因流动的中断之间存在很强的相关性。遗传分化（mtDNA φST = 0.902，微卫星 FST = 0.055：任一标记的基因同质性概率 p<0.001）、种群间的迁移者（少于 1%/代）缺失以及最近共同祖先的聚合计数估计表明，该系统主要海洋特征（200 万年前）的建立，特别是常年上升流细胞的加强和位置，是观察到的隔离背后最可能的机制。线粒体和核遗传标记的一致性表明，阿氏前鳍鲹的北部和南部本格拉种群的隔离和分化发生在很久以前，并一直持续到今天。这些发现表明，本格拉洋流系统可能是暖温鱼类基因流动的古老且不可渗透的屏障。
