Andrews Kimberly R, Norton Emily L, Fernandez-Silva Iria, Portner Elan, Goetze Erica
Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawai'i at Mānoa, Honolulu, HI, 96822, USA; School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK.
Mol Ecol. 2014 Nov;23(22):5462-79. doi: 10.1111/mec.12950.
Zooplanktonic taxa have a greater number of distinct populations and species than might be predicted based on their large population sizes and open-ocean habitat, which lacks obvious physical barriers to dispersal and gene flow. To gain insight into the evolutionary mechanisms driving genetic diversification in zooplankton, we developed eight microsatellite markers to examine the population structure of an abundant, globally distributed mesopelagic copepod, Haloptilus longicornis, at 18 sample sites across the Atlantic and Pacific Oceans (n = 761). When comparing our microsatellite results with those of a prior study that used a mtDNA marker (mtCOII, n = 1059, 43 sample sites), we unexpectedly found evidence for the presence of a cryptic species pair. These species were globally distributed and apparently sympatric, and were separated by relatively weak genetic divergence (reciprocally monophyletic mtCOII lineages 1.6% divergent; microsatellite FST ranging from 0.28 to 0.88 across loci, P < 0.00001). Using both mtDNA and microsatellite data for the most common of the two species (n = 669 for microsatellites, n = 572 for mtDNA), we also found evidence for allopatric barriers to gene flow within species, with distinct populations separated by continental landmasses and equatorial waters in both the Atlantic and Pacific Ocean basins. Our study shows that oceanic barriers to gene flow can act as a mechanism promoting allopatric diversification in holoplanktonic taxa, despite the high potential dispersal abilities and pelagic habitat for these species.
浮游动物类群拥有的独特种群和物种数量，比根据其庞大的种群规模和开阔海洋栖息地所预测的要多，开阔海洋栖息地缺乏明显的物理屏障来阻止扩散和基因流动。为了深入了解驱动浮游动物遗传多样化的进化机制，我们开发了8个微卫星标记，以研究一种分布广泛、数量丰富的中层桡足类动物——长角哈氏哲水蚤（Haloptilus longicornis）在横跨大西洋和太平洋的18个采样点的种群结构（n = 761）。当我们将微卫星分析结果与之前一项使用线粒体DNA标记（mtCOII，n = 1059，43个采样点）的研究结果进行比较时，意外地发现了存在一对隐性物种的证据。这些物种分布于全球，看似同域分布，且由相对较弱的遗传分化分隔开来（相互单系的mtCOII谱系差异为1.6%；微卫星FST在各基因座范围为0.28至0.88，P < 0.00001）。利用这两个物种中最常见的一个物种的线粒体DNA和微卫星数据（微卫星分析n = 669，线粒体DNA分析n = 572），我们还发现了物种内部基因流动存在异域屏障的证据，在大西洋和太平洋盆地，不同的种群被大陆陆地和赤道水域分隔开来。我们的研究表明，尽管这些全浮游生物类群具有很高的潜在扩散能力和远洋栖息地，但海洋中的基因流动屏障可作为促进其异域多样化的一种机制。
