Data from: Geographic isolation and larval dispersal shape seascape genetic patterns differently according to spatial scale

Genetic variation, as a basis of evolutionary change, allows species to adapt and persist in different climates and environments. Yet, a comprehensive assessment of the drivers of genetic variation at different spatial scales is still missing in marine ecosystems. Here, we investigated the influence of environment, geographic isolation, and larval dispersal on the variation in allele frequencies, using an extensive spatial sampling (47 locations) of the striped red mullet (Mullus surmuletus) in the Mediterranean Sea. Univariate multiple regressions were used to test the influence of environment (salinity and temperature), geographic isolation, and larval dispersal on Single Nucleotide Polymorphisms (SNPs) allele frequencies. We used Moran’s Eigenvector Maps (db-MEMs) and Asymmetric Eigenvector Maps (AEMs) to decompose geographic and dispersal distances in predictors representing different spatial scales. We found that salinity and temperature had only a weak effect on the variation in allele frequencies. Our results revealed the predominance of geographic isolation to explain variation in allele frequencies at large spatial scale (> 1,000km) while larval dispersal was the major predictor at smaller spatial scale (< 1,000km). Our findings stress the importance of including spatial scales to understand the drivers of spatial genetic variation. We suggest that larval dispersal allows to maintain gene flows at small to intermediate scale, while at broad scale, genetic variation may be mostly shaped by adult mobility, demographic history or multi-generational stepping stone dispersal. These findings bring out important spatial scale considerations to account for in the design of a protected areas network that would efficiently enhance protection and persistence capacity of marine species.遗传变异作为进化改变的基础，使得物种能够适应并存续于各类气候与环境之中。然而，海洋生态系统中针对不同空间尺度下遗传变异驱动因素的系统性评估仍存在空白。本研究针对地中海海域条纹红鲻（*Mullus surmuletus*）开展了覆盖47个采样点的大范围空间采样，借此探究环境因子、地理隔离以及幼体扩散对等位基因频率变异的影响。本研究采用单变量多元回归方法，检验了环境因子（盐度与温度）、地理隔离以及幼体扩散对单核苷酸多态性（Single Nucleotide Polymorphisms, SNPs）等位基因频率的影响。我们运用莫兰特征向量图（Moran’s Eigenvector Maps, db-MEMs）与非对称特征向量图（Asymmetric Eigenvector Maps, AEMs），对代表不同空间尺度的预测变量中的地理距离与扩散距离进行分解。研究结果显示，盐度与温度对等位基因频率变异仅存在微弱影响。本研究揭示：在大于1000公里的大空间尺度上，地理隔离对解释等位基因频率变异占据主导地位；而在小于1000公里的较小空间尺度中，幼体扩散则是主要的预测因子。上述研究结果强调了纳入空间尺度因素对于理解空间遗传变异驱动机制的重要性。我们提出，幼体扩散可维持中小尺度的基因流；而在大空间尺度下，遗传变异或主要由成体移动能力、种群历史或多代踏石扩散所塑造。这些研究结果为保护区网络的设计提供了关键的空间尺度考量依据，有助于高效提升海洋物种的保护成效与种群存续能力。