The mosaic nature of hybrid genomes is well recognized, but little is known of how they are shaped initially by patterns of breeding, selection, recombination and differential incompatibilities. On the small Galápagos island of Daphne Major, two species of Darwin's finches, Geospiza fortis and G. scandens, hybridize rarely and back-cross bidirectionally with little or no loss of fitness under conditions of plentiful food. We used whole-genome sequences to compare genomes from periods before and after successful interbreeding followed by back-crossing. We inferred extensive introgression from G. fortis to G. scandens on autosomes and mitochondria but not on the Z chromosome. The unique combination of long-term field observations and genomic data shows that the reduction of gene flow for Z-linked loci primarily reflects female-biased gene flow, arising from a hybrid-male disadvantage in competition for high-quality territories and mates, rather than from genetic incompatibilities at Z-linked loci.

中文翻译：

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女性偏爱的基因在两种达尔文雀科之间流动。

杂种基因组的镶嵌性质已广为人知，但鲜为人知的是它们最初是如何通过繁殖，选择，重组和差异性不相容性模式形成的。在达芙妮少校的加拉帕戈斯群岛小岛上，达尔文的两种雀科（Geopiza fortis和G. scandens）很少杂交，并且在充足的食物条件下双向杂交，几乎没有或没有丧失适应性。我们使用全基因组序列比较成功杂交和回交前后的时期的基因组。我们推断常染色体和线粒体从富通芽孢杆菌到scan线虫有广泛的基因渗入，但在Z染色体上却没有。长期现场观察和基因组数据的独特结合表明，Z连锁基因座的基因流量减少主要反映了女性偏向的基因流量，