Data from: Range-wide population genetic structure of the Caribbean sea fan coral, Gorgonia ventalina

The population structure of benthic marine organisms is of central relevance for the conservation and management of these often threatened species as well as an accurate understanding of their ecological and evolutionary dynamics. A growing body of evidence suggests that marine populations can be structured over short distances despite theoretically high dispersal potential. Yet the proposed mechanisms governing this structure vary, and existing empirical population genetic evidence is of insufficient taxonomic and geographic scope to allow strong general inferences. Here we describe the range-wide population genetic structure of an ecologically important Caribbean octocoral, Gorgonia ventalina. Genetic differentiation was positively correlated with geographic distance and negatively correlated with oceanographically-modeled dispersal probability throughout the range. Although we observed admixture across hundreds of kilometers, estimated dispersal is low, and populations can be differentiated across distances <2km. These results suggest that populations of G. ventalina may be evolutionarily coupled via gene flow but are largely demographically independent. Observed patterns of differentiation corroborate biogeographic breaks identified in other taxa (e.g. an east/west divide near Puerto Rico) and also identify population divides not discussed in previous studies (e.g. the Yucatan Channel). Across the range, diversity was positively correlated with latitude, consistent with a source/sink dynamic driven by ocean currents. High genotypic diversity and absence of clonemates indicate that sex is the primary reproductive mode for G. ventalina. A comparative analysis of the population structure of G. ventalina and its dinoflagellate symbiont, Symbiodinium, indicates that the dispersal of these symbiotic partners is not coupled, and symbiont transmission occurs horizontally.

底栖海洋生物（benthic marine organisms）的种群遗传结构（population genetic structure），对于这类常受威胁物种的保护与管理，以及精准理解其生态与进化动态，均具有核心意义。日益增多的研究证据表明，尽管理论上海洋种群具备极高的扩散潜力，但其种群结构仍可在短距离范围内形成分化。然而，调控此类种群结构的潜在机制尚无统一定论，且现有实证种群遗传学研究在分类类群与地理覆盖范围上均存在不足，难以支撑具有普适性的强推断。本研究针对一种生态意义重要的加勒比海八放珊瑚（octocoral）——帆柳珊瑚（Gorgonia ventalina），阐述了其全分布范围内的种群遗传结构。在整个分布区内，遗传分化程度与地理距离呈正相关，与海洋环流模型模拟的扩散概率呈负相关。尽管研究观测到数百公里范围内存在基因混合现象，但估算得到的扩散能力仍较低，且种群在距离小于2公里的尺度下即可出现遗传分化。上述结果表明，帆柳珊瑚的种群虽可通过基因流（gene flow）实现进化层面的耦合，但在种群统计层面基本相互独立。本研究观测到的分化模式，既验证了其他类群中已发现的生物地理断裂带（例如波多黎各附近的东西向分界），同时也识别出此前研究未提及的种群分界（例如尤卡坦海峡）。在全分布区内，遗传多样性与纬度呈正相关，这与洋流驱动的源-汇动态（source/sink dynamic）假说相符。较高的基因型多样性以及无克隆个体的现象，表明有性生殖是帆柳珊瑚的主要繁殖方式。对帆柳珊瑚与其鞭毛藻（dinoflagellate）共生体——虫黄藻（Symbiodinium）的种群结构开展的比较分析显示，二者共生伙伴的扩散并未同步，且共生体的传播方式为水平传播（horizontal transmission）。