Data from: Genomic islands of divergence are not affected by geography of speciation in sunflowers.

Genomic studies of speciation often report the presence of highly differentiated genomic regions interspersed within a milieu of weakly diverged loci. The formation of these speciation islands is generally attributed to reduced inter-population gene flow near loci under divergent selection, but few studies have critically evaluated this hypothesis. Here, we report on transcriptome scans among four recently diverged pairs of sunflower (Helianthus) species that vary in the geographical context of speciation. We find that genetic divergence is lower in sympatric and parapatric comparisons, consistent with a role for gene flow in eroding neutral differences. However, genomic islands of divergence are numerous and small in all comparisons, and contrary to expectations, island number and size are not significantly affected by levels of interspecific gene flow. Rather, island formation is strongly associated with reduced recombination rates. Overall, our results indicate that the functional architecture of genomes plays a larger role in shaping genomic divergence than does the geography of speciation.

物种形成的基因组研究通常会发现，在大量弱分化位点的背景中，散布着高度分化的基因组区域。这类物种形成岛（speciation islands）的形成机制，一般被归因于趋异选择位点附近的种群间基因流减弱，但目前鲜有研究对这一假说开展严谨验证。本研究针对四对新近分化的向日葵属（Helianthus）物种对展开转录组扫描，这些物种对的物种形成地理背景各不相同。研究结果显示，同域分布与邻域分布的物种对比较中，遗传分化程度更低，这与基因流可侵蚀中性分化的理论预期相符。然而，所有比较组中，分化的基因组岛数量繁多且规模较小；与此前预期相悖的是，基因组岛的数量与大小并未受到种间基因流水平的显著影响。与之相反，岛屿形成与重组率降低呈现极强的相关性。综合来看，我们的研究结果表明，基因组的功能架构对基因组分化的塑造作用，远大于物种形成的地理背景。