Ebdon Sam, Laetsch Dominik R, Vila Roger, Baird Stuart J E, Lohse Konrad
Institute of Ecology and Evolution, The University of Edinburgh, Edinburgh, United Kingdom.
Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain.
PLoS Genet. 2025 Apr 10;21(4):e1011655. doi: 10.1371/journal.pgen.1011655. eCollection 2025 Apr.
Many closely related species continue to hybridise after millions of generations of divergence. However, the extent to which current patterning in hybrid zones connects back to the speciation process remains unclear: does evidence for current multilocus barriers support the hypothesis of speciation due to multilocus divergence? We analyse whole-genome sequencing data to investigate the speciation history of the scarce swallowtails Iphiclidespodalirius and I . feisthamelii, which abut at a narrow ( ∼ 25 km) contact zone north of the Pyrenees. We first quantify the heterogeneity of effective migration rate under a model of isolation with migration, using genomes sampled across the range to identify long-term barriers to gene flow. Secondly, we investigate the recent ancestry of individuals from the hybrid zone using genome polarisation and estimate the coupling coefficient under a model of a multilocus barrier. We infer a low rate of long-term gene flow from I . feisthamelii into I . podalirius - the direction of which matches the admixture across the hybrid zone - and complete reproductive isolation across ≈ 33% of the genome. Our contrast of recent and long-term gene flow shows that regions of low recent hybridisation are indeed enriched for long-term barriers which maintain divergence between these hybridising sister species. This finding paves the way for future analysis of the evolution of reproductive isolation along the speciation continuum.
许多亲缘关系密切的物种在经历了数百万代的分化后仍继续杂交。然而，杂交区域当前的模式在多大程度上可追溯到物种形成过程仍不清楚：当前多位点障碍的证据是否支持因多位点分化导致物种形成的假说？我们分析全基因组测序数据，以研究稀有的燕尾蝶Iphiclides podalirius和I. feisthamelii的物种形成历史，它们在比利牛斯山脉以北一个狭窄（约25公里）的接触区域相邻。我们首先在具有迁移的隔离模型下量化有效迁移率的异质性，使用在整个分布范围内采样的基因组来识别基因流动的长期障碍。其次，我们使用基因组极化研究杂交区域个体的近期祖先，并在多位点障碍模型下估计耦合系数。我们推断从I. feisthamelii到I. podalirius的长期基因流动率较低——其方向与杂交区域的混合方向一致——并且在约33%的基因组中存在完全生殖隔离。我们对近期和长期基因流动的对比表明，近期杂交率低的区域确实富含维持这些杂交姐妹物种之间分化的长期障碍。这一发现为未来分析沿物种形成连续统的生殖隔离进化铺平了道路。
