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.底栖海洋生物的种群结构，对于这类常受威胁物种的保护与管理，以及精准解析其生态与进化动态，均具有核心意义。日益增多的研究证据表明，尽管海洋种群理论上具备较高的扩散潜力，但其种群结构仍可在短距离范围内形成分化。然而，目前提出的调控此类种群结构的机制尚不统一，且现有实证种群遗传学研究在分类学与地理覆盖范围上存在局限，难以得出强有力的普遍性推论。本研究描述了加勒比海生态重要性八放珊瑚——紫柳珊瑚（Gorgonia ventalina）的全分布区种群遗传结构。在该物种的整个分布区内，遗传分化程度与地理距离呈正相关，与海洋环流模型预测的扩散概率呈负相关。尽管研究观察到数百公里范围内存在基因混合，但估算得到的扩散水平仍然较低，种群在小于2公里的距离内即可出现遗传分化。上述结果表明，紫柳珊瑚的种群或许可通过基因流实现进化层面的耦合，但在种群动态上基本相互独立。本研究观测到的遗传分化模式，既验证了其他生物类群中已发现的生物地理分界（例如波多黎各附近的东西向分化带），同时也揭示了此前研究未曾提及的种群分界（例如尤卡坦海峡）。在整个分布区内，遗传多样性与纬度呈正相关，这与洋流驱动的源-汇动态假说相符。较高的基因型多样性以及无性系个体的缺失，表明有性生殖是紫柳珊瑚的主要繁殖方式。对紫柳珊瑚与其共生甲藻（Symbiodinium）的种群结构开展的对比分析显示，二者的扩散过程并未耦合，且共生体通过水平传播方式完成定植。