Data from: Disentangling the influence of mutation and migration in clonal seagrasses using the Genetic Distance Spectrum for microsatellites

The recurrent lack of Isolation By Distance (IBD) reported at regional scale in seagrass species was recently suggested to stem from stochastic events of large scale dispersal. We explored the usefulness of phylogenetic information contained in microsatellite loci to test this hypothesis by using the Genetic Distance Spectrum (GDS) on databases containing respectively 7 and 9 microsatellites genotypes for 1541 sampling units of Posidonia oceanica and 1647 of Cymodocea nodosa. The simultaneous increase of microsatellite and geographic distances that emerges reveals a coherent pattern of IBD in contrast to the chaotic pattern previously described using allele frequencies, in particular for the long-lived P. oceanica. These results suggest that the lack of IBD, rather than the resulting from rare events of large scale dispersal, reflects at least for some species a stronger influence of mutation over migration at the scale of the distribution range. The global distribution of genetic polymorphism may therefore result predominantly from ancient events of step-by-step (re)colonization followed by local recruitment and clonal growth, rather than contemporary gene flow. The analysis of GDS appears useful to unravel the evolutionary forces influencing the dynamics and evolution at distinct temporal and spatial scales by accounting for phylogenetic information borne by microsatellites, under an appropriate mutation model. This finding adds nuance to the generalization of the influence of large scale dispersal on the dynamics of seagrasses.

此前有研究提出，区域尺度下海草物种频繁观测到的距离隔离效应（Isolation By Distance, IBD）缺失现象，近期被认为源于大规模扩散的随机事件。本研究利用两套数据库开展假说检验：其中一套包含1541个波西多尼亚海草（Posidonia oceanica）采样单元的7个微卫星基因型，另一套则包含1647个诺氏海草（Cymodocea nodosa）采样单元的9个微卫星基因型，借此采用遗传距离谱（Genetic Distance Spectrum, GDS）分析，探究微卫星位点所携带的系统发育信息的应用价值。研究结果显示，微卫星遗传距离与地理距离同步增加，这一发现揭示出一致的距离隔离效应模式，与此前基于等位基因频率所描述的混沌模式形成显著差异，该现象在长寿的波西多尼亚海草中尤为突出。上述结果表明，距离隔离效应的缺失，并非一概由大规模扩散的稀有事件导致；至少对于部分物种而言，其反映了在物种分布范围尺度上，突变对种群分化的影响强于迁移作用。因此，遗传多态性的全球分布格局，可能主要源自逐步（再）定殖的古老演化事件，后续伴随局域种群补充与克隆生长，而非当代的基因流过程。在适配的突变模型框架下，借助微卫星所携带的系统发育信息，对遗传距离谱的分析能够有效揭示不同时空尺度下影响种群动态与演化的进化力量。这一发现为“大规模扩散对海草种群动态的影响”这一普遍性结论增添了更精细的认知维度。