Data from: Neutral and selective processes drive population differentiation for Iris hexagona

Gene flow among widespread populations can be reduced by geographical distance or by divergent selection resulting from local adaptation. In this study, we tested for the divergence of phenotypes and genotypes among 8 populations of Iris hexagona. Using a genotyping-by-sequencing approach, we generated a panel of 750 single nucleotide polymorphisms (SNPs) and used population genetic analyses to determine what may affect patterns of divergence across I. hexagona populations. Specifically, genetic differentiation was compared between populations at neutral and nonneutral SNPs and detected significant differences between the 2 types of markers. We then asked whether loci with the strongest degree of population genetic differentiation were also the loci with the strongest association to morphology or climate differences, allowing us to test if pollinators or climate drive population differentiation or some combination of both. We found 2 markers that were associated with morphology and 1 marker associated with 2 of the environmental variables, which were also identified in the outlier analysis. We then show that the SNPs putatively under selection were positively correlated with both geographic distance and phenotypic distance, albeit weakly to phenotypic distance. Moreover, neutral SNPs were only correlated with geographic distance and thus isolation-by-distance was observed for neutral SNPs. Our data suggest that both deterministic and neutral processes have contributed to the evolutionary trajectory of I. hexagona populations.

广布种群间的基因流可因地理距离，或是本地适应所产生的歧化选择而受到抑制。本研究以六棱鸢尾（Iris hexagona）的8个种群为对象，开展了表型与基因型分化的检测分析。我们采用基因组分型测序（genotyping-by-sequencing）技术，构建了包含750个单核苷酸多态性（single nucleotide polymorphisms, SNPs）的位点面板，并通过种群遗传分析，探究影响六棱鸢尾种群分化模式的潜在因素。具体而言，我们对比了中性与非中性SNPs位点的种群间遗传分化水平，发现这两类分子标记之间存在显著差异。随后我们进一步探究：种群遗传分化程度最高的位点，是否同时与形态差异或气候差异存在最强关联，以此检验种群分化是否由传粉者、气候，或是二者共同作用所驱动。研究结果显示，2个分子标记与形态特征相关，另有1个分子标记与2项环境变量相关，这些标记同时在离群位点分析中被鉴定得到。我们还证实，推测处于选择压力下的SNPs位点与地理距离、表型距离均呈正相关，尽管其与表型距离的相关性较弱。此外，中性SNPs仅与地理距离存在相关性，表明中性位点呈现出典型的距离隔离效应。本研究数据表明，确定性进化过程与中性进化过程共同塑造了六棱鸢尾种群的演化轨迹。