Data from: On the spatial scale of dispersal in coral reef fishes

Marine biologists have gone through a paradigm shift, from the assumption that marine populations are largely ‘open’ due to extensive larval dispersal to the realization that marine dispersal is ‘more restricted than previously thought’. Yet, population genetic studies often reveal low levels of genetic structure across large geographic areas. On the other side, more direct approaches such as mark-recapture provide evidence of localized dispersal. To what extent can direct and indirect studies of marine dispersal be reconciled? One approach consists in applying genetic methods that have been validated with direct estimates of dispersal. Here, we use such an approach - genetic isolation-by-distance between individuals in continuous populations - to estimate the spatial scale of dispersal in five species of coral reef fish presenting low levels of genetic structure across the Caribbean. Individuals were sampled continuously along a 220 km transect following the Mesoamerican Barrier Reef, population densities were estimated from surveys covering 17 200 m2 of reef, and samples were genotyped at a total of 58 microsatellite loci. A small but positive isolation-by-distance slope was observed in the five species, providing mean parent-offspring dispersal estimates ranging between 7 and 42 km (CI 1-113 km), and suggesting that there might be a correlation between minimum/maximum PLD and dispersal in coral reef fishes. Coalescent-based simulations indicate that these results are robust to a variety of dispersal distributions and sampling designs. We conclude that low levels of genetic structure across large geographic areas are not necessarily indicative of extensive dispersal at ecological timescales.海洋生物学家的研究范式已发生根本性转变：此前学界普遍认为，由于幼体广泛扩散，海洋种群整体上呈“开放”状态；而如今学界逐渐意识到，海洋扩散的范围实则比此前预想的更为受限。然而，种群遗传学研究却常常显示，在大范围地理区域内，种群的遗传结构分化程度极低。与之相对，标记重捕法（mark-recapture）等更为直接的研究方法，则为局域性扩散提供了实证支撑。那么，海洋扩散的直接与间接研究结果，究竟能在多大程度上达成统一？ 一种可行的解决方案是采用经扩散直接估算验证过的遗传学方法。本研究即采用此类方法——基于连续种群个体间的逐距离遗传分化（isolation-by-distance）模型——对加勒比海范围内5个遗传结构分化程度较低的珊瑚礁鱼类物种的扩散空间尺度进行估算。 研究团队沿中美洲堡礁（Mesoamerican Barrier Reef）设置了总长220公里的连续样带开展个体采样；通过覆盖17200平方米礁区的调查估算种群密度；并对总计58个微卫星位点（microsatellite loci）进行基因分型。 5个物种均呈现出微弱但显著的逐距离遗传分化斜率，据此估算的亲代-子代扩散距离均值介于7至42公里之间，置信区间（CI）为1至113公里，且结果暗示珊瑚礁鱼类的浮游幼体持续时间（PLD, pelagic larval duration）的最值与扩散规模间或存在相关性。 基于溯祖理论的模拟实验表明，上述结果在多种扩散分布模式与采样设计下均保持稳健。 本研究最终得出结论：大范围地理区域内的低遗传结构分化，未必意味着生态时间尺度下存在广泛的种群扩散。