Data from: Ecological dispersal barrier across the equatorial Atlantic in a migratory planktonic copepod

Resolving the large-scale genetic structure of plankton populations is important to understanding their responses to climate change. However, few studies have reported on the presence and geographic extent of genetically distinct populations of marine zooplankton at ocean-basin scales. Using mitochondrial sequence data (mtCOI, 718 animals) from 18 sites across a basin-scale Atlantic transect (39 N–40 S), we show that populations of the dominant migratory copepod, Pleuromamma xiphias, are genetically subdivided across subtropical and tropical waters (global FST = 0.15, global Phi-ST = 0.21, both P < 0.00001), with a major genetic break observed in the equatorial Atlantic (between gyre FCT and Phi-CT = 0.23, P < 0.005). This equatorial region of strong genetic transition coincides with an area of low abundance for the species. Transitional regions between the subtropical gyres and the equatorial province also harbor a distinct mitochondrial clade (clade 2), have higher haplotype and nucleotide diversities relative to the northern and/or southern subtropical gyres (e.g., mean h = 0.831 EQ, 0.742 North, 0.594 South, F2,11 = 20.53, P < 0.001), and are genetically differentiated from the majority of sites in the central gyre and temperate zones of the same hemisphere (significant pairwise Phi-ST 0.038–0.267, 79% significant). Our observations support the hypothesis that regions of low abundance within species mark areas of suboptimal habitat that serve as dispersal barriers for marine plankton, and we suggest that this may be a dominant mechanism driving the large-scale genetic structure of zooplankton species. Our results also demonstrate the potential importance of the Atlantic equatorial province as a region of evolutionary novelty for the holoplankton.

解析浮游生物种群的大规模遗传结构，对于理解其对气候变化的响应至关重要。然而，目前鲜有研究在大洋盆地尺度上报道海洋浮游动物的遗传分化种群及其地理分布范围。本研究基于横跨大西洋盆尺度样带（北纬39°至南纬40°）18个采样点的线粒体序列数据（mtCOI，即线粒体细胞色素氧化酶亚基I，共718个个体），发现优势洄游性桡足类物种Pleuromamma xiphias的种群在亚热带与热带水域存在遗传分化（整体FST=0.15，整体Phi-ST=0.21，二者P值均<0.00001），并在大西洋赤道区域观测到显著的遗传断裂（环流间FCT=0.23、Phi-CT=0.23，P<0.005）。该遗传过渡强烈的赤道区域，恰好对应该物种丰度较低的海域。亚热带环流与赤道生物区系之间的过渡区域同样存在独特的线粒体进化枝（进化枝2），其单倍型多样性与核苷酸多样性均高于南北亚热带环流区（例如，赤道区平均单倍型多样性h=0.831，北区为0.742，南区为0.594；F2,11=20.53，P<0.001），且与同半球中部环流区及温带区域的多数采样点存在遗传分化（成对Phi-ST值介于0.038~0.267之间，79%的检验结果显著）。本研究结果支持以下假说：物种种群丰度较低的区域代表了次优生境，可作为海洋浮游生物的扩散障碍；我们推测这可能是驱动浮游动物物种形成大规模遗传结构的主导机制。此外，本研究结果还表明，大西洋赤道生物区系作为终生浮游生物（holoplankton）的进化创新区域，其潜在重要性不容忽视。