High levels of population differentiation are a common demographic pattern in syngnathids, even at small geographical scales. This is probably the end result of the common life history traits observed within the family, involving limited dispersal capabilities and strong habitat dependency. The worm pipefish, Nerophis lumbriciformis, which displays all these characteristics, also presents an additional variable potentially able to promote population differentiation: high sexual selection intensity, especially at the extremes of its distribution. Nevertheless, an early life pelagic stage, which presumable allows for admixture, could prevent population structuring. Here, we assessed the phylogeography of N. lumbriciformis through the amplification of the cytochrome b, 12S and 16S rDNA mitochondrial markers as well as the rhodopsin nuclear marker, performed upon 119 individuals. We observed a genetically homogeneous population with indications of extensive gene flow. We tentatively attribute this finding to the dispersal potential of the species' pelagic larvae, supported by marine currents acting as major dispersal vectors. We also detected a signal of expansion towards the poles, consistent with the current climate change scenario. Despite the marked latitudinal differences in the phenotype of reproducing worm pipefish, the absence of clear population structuring suggests that phenotypic plasticity can have a significant role in the expression of sexual selection-related traits.

中文翻译：

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强烈的性别选择不会在具有高扩散潜力的鱼类物种中诱导种群分化：蠕虫尖嘴鱼 Nerophis lumbriciformis（Teleostei：Syngnathidae）的奇怪案例

高水平的种群分化是合颚纲动物的常见人口统计模式，即使在较小的地理范围内也是如此。这可能是在家庭内观察到的共同生活史特征的最终结果，涉及有限的传播能力和强烈的栖息地依赖性。蠕虫尖嘴鱼，Nerophis lumbriciformis，显示了所有这些特征，也提供了一个可能促进种群分化的附加变量：高性选择强度，特别是在其分布的极端情况下。然而，可能允许混合的早期生活中上层阶段可能会阻止种群结构。在这里，我们通过细胞色素 b、12S 和 16S rDNA 线粒体标记以及视紫质核标记的扩增评估了 N. lumbriciformis 的系统地理学，对 119 个人执行。我们观察到具有广泛基因流动迹象的遗传同质种群。我们暂时将这一发现归因于该物种的远洋幼虫的传播潜力，并得到了作为主要传播媒介的海流的支持。我们还检测到向极地扩张的信号，与当前的气候变化情景一致。尽管繁殖蠕虫尖嘴鱼的表型存在显着的纬度差异，但缺乏明确的种群结构表明表型可塑性在性选择相关性状的表达中具有重要作用。远洋幼虫，由作为主要传播媒介的海流支持。我们还检测到向极地扩张的信号，与当前的气候变化情景一致。尽管繁殖蠕虫尖嘴鱼的表型存在显着的纬度差异，但缺乏明确的种群结构表明表型可塑性在性选择相关性状的表达中可能具有重要作用。远洋幼虫，由作为主要传播媒介的海流支持。我们还检测到向极地扩张的信号，与当前的气候变化情景一致。尽管繁殖蠕虫尖嘴鱼的表型存在显着的纬度差异，但缺乏明确的种群结构表明表型可塑性在性选择相关性状的表达中具有重要作用。