Department of Biology, University of Puerto Rico, Rio Piedras, Puerto Rico.
Department of Biological Sciences, Mississippi State University, Mississippi State, USA.
Evolution. 2021 Sep;75(9):2251-2268. doi: 10.1111/evo.14272. Epub 2021 Jun 6.
Hybridizing species provide a powerful system to identify the processes that shape genomic variation and maintain species boundaries. However, complex histories of isolation, gene flow, and selection often generate heterogeneous genomic landscapes of divergence that complicate reconstruction of the speciation history. Here, we explore patterns of divergence to reconstruct recent speciation in the erato clade of Heliconius butterflies. We focus on the genomic landscape of divergence across three contact zones of the species H. erato and H. himera. We show that these hybridizing species have an intermediate level of divergence in the erato clade, which fits with their incomplete levels of reproductive isolation. Using demographic modeling and the relationship between admixture and divergence with recombination rate variation, we reconstruct histories of gene flow, selection, and demographic change that explain the observed patterns of genomic divergence. We find that periods of isolation and selection within populations, followed by secondary contact with asymmetrical gene flow are key factors in shaping the heterogeneous genomic landscapes. Collectively, these results highlight the effectiveness of demographic modeling and recombination rate estimates to disentangling the distinct contributions of gene flow and selection to patterns of genomic divergence.
杂交种提供了一个强大的系统，可以识别塑造基因组变异和维持物种边界的过程。然而，隔离、基因流动和选择的复杂历史通常会产生异质的基因组分化景观，从而使物种形成历史的重建变得复杂。在这里，我们探讨了分化模式，以重建 Heliconius 蝴蝶的 erato 进化枝中最近的物种形成。我们专注于三种 H. erato 和 H. himera 物种接触区的基因组分化景观。我们表明，这些杂交种在 erato 进化枝中具有中等水平的分化，这与它们不完全的生殖隔离水平相符。通过人口统计学建模以及杂种形成与重组率变化之间的关系，我们重建了基因流动、选择和人口变化的历史，这些历史解释了观察到的基因组分化模式。我们发现，种群内的隔离和选择时期，然后是不对称基因流的二次接触，是形成异质基因组景观的关键因素。总的来说，这些结果强调了人口统计学建模和重组率估计的有效性，可以区分基因流动和选择对基因组分化模式的不同贡献。
