Shared selective pressure and local genomic landscape lead to repeatable patterns of genomic divergence in sunflowers

The repeated evolution of traits in organisms facing similar environmental conditions is considered to be fundamental evidence for the role of natural selection in moulding phenotypes. Yet, aside from case studies of parallel evolution and its genetic basis, the repeatability of evolution at the level of the whole genome remains poorly characterized. Here, through the use of transcriptome sequencing, we examined genomic divergence for three pairs of sister species of sunflowers. Two of the pairs (Helianthus petiolaris – H. debilis and H. annuus – H. argophyllus) have diverged along a similar latitudinal gradient and presumably experienced similar selective pressure. In contrast, a third species pair (H. exilis – H. bolanderi) diverged along a longitudinal gradient. Analyses of divergence, as measured in terms of FST, indicated little repeatability across the three pairs of species for individual genetic markers (SNPs), modest repeatability at the level of individual genes and the highes...生物体在相似环境条件下反复演化出相同性状，被视为自然选择塑造表型的核心证据。然而，除平行演化及其遗传基础的个案研究外，全基因组层面的演化可重复性仍未得到充分解析。本研究通过转录组测序（transcriptome sequencing），对3对向日葵姐妹物种的基因组分化展开分析。其中2对物种（狭叶向日葵*Helianthus petiolaris* – 滨海向日葵*H. debilis*，以及普通向日葵*H. annuus* – 银叶向日葵*H. argophyllus*）沿相似的纬度梯度发生分化，推测经历了相似的选择压力。与之相对，第三对物种（纤细向日葵*H. exilis* – 博兰德向日葵*H. bolanderi*）沿经度梯度发生分化。以FST（固定化指数）为指标开展的分化分析显示，3对物种在单个遗传标记（单核苷酸多态性，SNPs）层面几乎无重复演化特征，在单个基因层面的重复特征较为适中，而最高...