Data from: Exploring neutral and adaptive processes in expanding populations of gilthead sea bream, Sparus aurata L., in the North-East Atlantic

Recent studies in empirical population genetics have highlighted the importance of taking into account both neutral and adaptive genetic variation in characterizing microevolutionary dynamics. Here we explore the genetic population structure and the footprints of selection in four populations of the warm-temperate coastal fish, the gilthead sea bream (Sparus aurata), whose recent northward expansion has been linked to climate change. Samples were collected at four Atlantic locations, including Spain, Portugal, France and the South of Ireland, and genetically assayed using a suite of species-specific markers, including 15 putatively neutral microsatellites and 23 Expressed Sequence Tag-linked (ESTs) markers, as well as a portion of the mitochondrial DNA (mtDNA) Control Region. Two of the putatively neutral markers, Bld-10 and Ad-10, bore signatures of strong directional selection, particularly in the newly established Irish population, though the potential 'surfing effect' of rare alleles at the edge of the expansion front was also considered. Analyses after the removal of these loci suggest low but significant population structure likely affected by some degree of gene flow counteracting random genetic drift. No signal of historic divergence was detected at mtDNA. BLAST searches conducted with all 38 markers used failed to identify specific genomic regions associated to adaptive functions. However, the availability of genomic resources for this commercially valuable species is rapidly increasing, bringing us closer to the understanding of the interplay between selective and neutral evolutionary forces, shaping population divergence of an expanding species in a heterogeneous milieu.实证群体遗传学（empirical population genetics）的近期研究强调，在解析微进化动态时，需同时考量中性遗传变异与适应性遗传变异的重要性。本研究针对暖温带近海鱼类金头鲷（Sparus aurata）的四个种群，探究其遗传群体结构与选择印记——该物种近年的北向扩张与气候变化存在关联。研究样本采集自大西洋沿岸的四个区域，涵盖西班牙、葡萄牙、法国与爱尔兰南部；采用一系列物种特异性标记开展基因分型，包括15个推定中性的微卫星（microsatellites）标记、23个表达序列标签关联（Expressed Sequence Tag-linked, ESTs）标记，以及线粒体DNA（mtDNA）控制区的一段序列。其中两个推定中性标记Bld-10与Ad-10呈现出强烈定向选择的特征，这一现象在新近建立的爱尔兰种群中尤为显著；同时研究也考量了扩张前沿边缘稀有等位基因潜在的等位基因冲浪效应（surfing effect）。移除这两个位点后的分析结果显示，种群结构整体较弱但仍具有统计学显著性，其大概率受到一定程度基因流的影响，该基因流可抵消随机遗传漂变的作用。在线粒体DNA控制区中未检测到历史分化的信号。对本次使用的全部38个标记开展的BLAST搜索未能鉴定出与适应性功能相关的特定基因组区域。然而，这一具有重要商业价值的物种种基因组资源的可用性正快速提升，这将帮助我们进一步理解选择与中性进化力量之间的相互作用——正是这种相互作用塑造了异质环境中扩张物种种群的分化过程。