Recent hybrids recapitulate ancient hybrid outcomes

Genomic outcomes of hybridization depend on selection and recombination in hybrids. Whether these processes have similar effects on hybrid genome composition in contemporary hybrid zones versus ancient hybrid lineages is unknown. Here we show that patterns of introgression in a contemporary hybrid zone in Lycaeides butterflies predict patterns of ancestry in geographically adjacent, older hybrid populations. We find a particularly striking lack of ancestry from one of the hybridizing taxa, Lycaeides melissa, on the Z chromosome in both the old and contemporary hybrids. The same pattern of reduced L. melissa ancestry on the Z chromosome is seen in two other ancient hybrid lineages. More generally, we find that patterns of ancestry in old or ancient hybrids are remarkably predictable from contemporary hybrids, which suggests selection and recombination affect hybrid genomes in a similar way across disparate time scales and during distinct stages of speciation and species breakdown.

 
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杂交（hybridization）的基因组学结果取决于杂交种中的选择与重组过程。这些过程对当代杂交带与古老杂交谱系中杂交基因组组成的影响是否相似，目前尚不清楚。本研究表明，灰蝶属（Lycaeides）蝴蝶当代杂交带中的基因渗入（introgression）模式可预测地理上相邻的较古老杂交种群的祖先模式。我们发现一个特别显著的现象：在古老和当代杂交种的Z染色体（Z chromosome）上，均缺乏来自杂交类群之一的Melissa灰蝶（Lycaeides melissa）的祖先成分。在另外两个古老杂交谱系中，也观察到Z染色体上Melissa灰蝶祖先成分减少的相同模式。更普遍地说，我们发现古老杂交种的祖先模式可通过当代杂交种显著预测，这表明选择与重组在不同时间尺度以及物种形成（speciation）与物种分化的不同阶段，对杂交基因组的影响方式相似。