Graduate Program in Oceanography, Department of Oceanography, University of Concepción, PO Box 160, Barrio Universitario s/n Concepción, Concepción, 4030000, Chile.
Instituto Milenio de Oceanografía (IMO) and Department of Oceanography, Faculty of Natural and Oceanographic Sciences, Universidad de Concepción, PO Box 160 C, Barrio Universitario s/n Concepción, Concepción, 4030000, Chile.
Sci Rep. 2020 Jan 24;10(1):1115. doi: 10.1038/s41598-019-56935-5.
Across boundary currents, zooplankton are subject to strong oceanographic gradients and hence strong selective pressures. How such gradients interact with the speciation process of pelagic organisms is still poorly understood in the open ocean realm. Here we report on genetic diversity within the pelagic copepod Pleuromamma abdominalis in the poorly known Southeast Pacific region, with samples spanning an ocean gradient from coastal upwelling to the oligotrophic South Pacific Subtropical Gyre. We assessed variation in fragments of the mitochondrial (mt) genes cytochrome c oxidase subunit I (COI) and Cytochrome b as well as in the nuclear internal transcribed spacer (ITS) region and 28 S rRNA. Phylogenetic analyses revealed the presence of 8 divergent lineages occurring across the gradient with genetic distances in the range of 0.036 and 0.44 (mt genes), and GMYC species delimitation methods support their inference as distinct (undescribed) species. Genetic lineages occurring across the zonal gradient showed strong genetic structuring, with the presence of at least two new lineages within the coastal upwelling zone, revealing an unexpectedly high level of endemism within the Humboldt Current System. Multivariate analyses found strong correlation between genetic variation and surface chlorophyll-a and salinity, suggesting an important role for hydrographic gradients in maintaining genetic diversity. However, the presence of cryptic lineages within the upwelling zone cannot be easily accounted for by environmental heterogeneity and poses challenging questions for understanding the speciation process for oceanic zooplankton.
跨越边界流，浮游动物受到强烈的海洋梯度影响，因此受到强烈的选择压力。这些梯度如何与浮游生物的物种形成过程相互作用，在开阔海域中仍然知之甚少。在这里，我们报告了在南太平洋副热带环流等贫营养海域中，沿海洋梯度从沿海上升流到贫营养的东南太平洋，浮游桡足类 Pleuromamma abdominalis 的遗传多样性。我们评估了线粒体（mt）基因细胞色素 c 氧化酶亚基 I（COI）和细胞色素 b 以及核内转录间隔区（ITS）和 28S rRNA 的片段的变异。系统发育分析显示，在梯度范围内存在 8 个不同的谱系，遗传距离在 0.036 和 0.44（mt 基因）之间，GMYC 物种划分方法支持它们作为不同（未描述）物种的推断。在带状梯度上发生的遗传谱系表现出强烈的遗传结构，在沿海上升流区至少存在两个新的谱系，这揭示了洪堡海流系统内出人意料的高特有种水平。多元分析发现遗传变异与表观光合叶绿素-a 和盐度之间存在强烈相关性，表明水文学梯度在维持遗传多样性方面起着重要作用。然而，上升流区中隐生谱系的存在不能简单地用环境异质性来解释，这对理解海洋浮游动物的物种形成过程提出了挑战。
