Data from: Contrasting patterns of genome-wide polymorphism in the native and invasive range of the marine mollusk Crepidula fornicata

Selection processes are believed to be an important evolutionary driver behind the successful establishment of non-indigenous species, however evidence is still scarce. Genome-scans have often identified loci with atypical patterns of genetic differentiation (i.e. outliers) indicative of selection processes. Using microsatellite- and AFLP-based genome-scans, we looked for evidence of post-introduction selection in the mollusk Crepidula fornicata, native from the northwestern Atlantic and introduced in the northeastern Atlantic and northeastern Pacific during the 19th and 20th centuries. We examined 683 individuals from 7 native and 15 introduced populations spanning the latitudinal introduction and native ranges of the species. Our results showed the high genetic diversity in all populations with little genetic structure between the two ranges, a pattern typical of marine invaders. Analyzing 344 loci, no outliers were detected between introduced and native populations or within introduced populations. The genomic sampling may have been insufficient to reveal selection especially if it acts on traits determined by a few genes. Eight outliers were however identified within the native range, underlining a genetic singularity congruent with a well-known biogeographic break along the Florida. Our results call into question the relevance of AFLP genome-scans in detecting adaptation on the time-scale of biological invasions: genome-scans often reveal long-term adaptation involving numerous genes throughout the genome but seem less effective in detecting recent adaptation from pre-existing variation on polygenic traits. This study advocates other methods to detect selection effects during biological invasions – on phenotypic traits, although genome-scans may remain useful for elucidating introduction histories.人们普遍认为，选择过程是非土著物种成功定殖背后的重要进化驱动力，但相关证据仍较为匮乏。基因组扫描（Genome-scans）通常可筛选出具有非典型遗传分化模式的位点（即异常位点），这类位点可作为选择过程的指示标志。本研究借助基于微卫星（microsatellite）与AFLP（扩增片段长度多态性）的基因组扫描技术，针对美洲履螺（*Crepidula fornicata*）开展了引入后选择作用的证据搜寻工作；该物种原生分布于西北大西洋，并于19至20世纪被引入东北大西洋与东北太平洋海域。我们共采集了覆盖该物种原生与引入分布纬度范围的7个原生种群与15个引入种群的683个个体进行分析。研究结果显示，所有种群均具有较高的遗传多样性，且两类分布范围间的遗传结构差异极小，这一模式符合海洋入侵物种的典型特征。通过对344个位点的分析，我们未在引入种群与原生种群之间，或是引入种群内部检测到异常位点。本次基因组采样可能不足以揭示选择作用，尤其是当选择作用仅针对少数基因调控的性状时。但在原生分布范围内共检测到8个异常位点，这一遗传特异性与佛罗里达沿岸知名的生物地理间断现象相吻合。本研究结果对AFLP基因组扫描在生物入侵时间尺度下检测适应性演化的适用性提出了质疑：基因组扫描通常可揭示涉及全基因组众多基因的长期适应性演化，但在检测多基因性状中基于预先存在变异的近期适应性演化方面效果欠佳。尽管基因组扫描在阐明物种引入历史方面仍具有应用价值，但本研究倡导采用其他方法来检测生物入侵过程中的选择作用——尤其是针对表型性状的检测方法。