Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
Department of Biological Sciences, Kent State University, Kent, OH, USA.
Nat Ecol Evol. 2020 Jul;4(7):979-986. doi: 10.1038/s41559-020-1183-9. Epub 2020 May 4.
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.
杂种基因组的镶嵌性质是众所周知的，但对于它们最初是如何通过繁殖、选择、重组和差异不相容性的模式形成的，人们知之甚少。在加拉帕戈斯小岛上的达芙妮大岛，两种达尔文雀，即强壮地雀和攀爬地雀，很少杂交，并且在食物充足的条件下，双向回交几乎没有或没有适应度的损失。我们使用全基因组序列比较了成功杂交后回交前后的基因组。我们推断出，在常染色体和线粒体上，来自强壮地雀的广泛基因渗入到攀爬地雀中，但在 Z 染色体上则没有。长期实地观察和基因组数据的独特组合表明，Z 连锁基因座的基因流减少主要反映了雌性偏向的基因流，这是由于杂交雄雀在争夺高质量领地和配偶时处于劣势，而不是由于 Z 连锁基因座上的遗传不相容性。
