Data from: Genomic evidence for the parallel evolution of coastal forms in the Senecio lautus complex

Instances of parallel ecotypic divergence where adaptation to similar conditions repeatedly cause similar phenotypic changes in closely related organisms are useful for studying the role of ecological selection in speciation. Here we used a combination of traditional and next generation genotyping techniques to test for the parallel divergence of plants from the Senecio lautus complex, a phenotypically variable groundsel that has adapted to disparate environments in the South Pacific. Phylogenetic analysis of a broad selection of Senecio species showed that members of the S. lautus complex form a distinct lineage that has diversified recently in Australasia. An inspection of thousands of polymorphisms in the genome of 27 natural populations from the S. lautus complex in Australia revealed a signal of strong genetic structure independent of habitat and phenotype. Additionally, genetic differentiation between populations was correlated with the geographical distance separating them, and the genetic diversity of populations strongly depended on geographical location. Importantly, coastal forms appeared in several independent phylogenetic clades, a pattern that is consistent with the parallel evolution of these forms. Analyses of the patterns of genomic differentiation between populations further revealed that adjacent populations displayed greater genomic heterogeneity than allopatric populations and are differentiated according to variation in soil composition. These results are consistent with a process of parallel ecotypic divergence in face of gene flow.

在亲缘关系相近的生物类群中，若适应相似环境的过程反复引发趋同表型变化，这类平行生态型分化（parallel ecotypic divergence）实例，可为探究生态选择在物种形成中的作用提供重要支撑。本研究结合传统基因分型技术与新一代基因分型技术（next generation genotyping techniques），对来自千里光复合群（Senecio lautus complex）的植物开展平行生态型分化检测；该类群为一类表型多样的千里光属（Senecio）植物，已适应南太平洋地区迥异的生境。对多个千里光属物种的系统发育分析显示，千里光复合群构成一个独立演化支系，且近期在澳大拉西亚地区发生了快速辐射分化。通过对澳大利亚境内千里光复合群27个自然种群的基因组中数千个多态性位点进行分析，结果显示存在显著的遗传结构分化，且该分化与生境及表型均无关联。此外，种群间的遗传分化程度与地理隔离距离呈显著正相关，而种群的遗传多样性则强烈依赖于其所处的地理位置。值得注意的是，海岸生态型在多个独立的系统发育支簇中均有出现，该模式与这类生态型的平行演化特征相符。对种群间基因组分化模式的进一步分析显示，邻域种群间的基因组异质性显著高于异域种群，且种群分化与土壤组分的差异密切相关。上述研究结果与“存在基因交流情况下仍发生平行生态型分化”的演化过程相符。