Department of Biosciences, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Oslo, Norway.
Nat Ecol Evol. 2018 Mar;2(3):549-556. doi: 10.1038/s41559-017-0437-7. Epub 2018 Jan 15.
Hybridization is an important source of variation; it transfers adaptive genetic variation across species boundaries and generates new species. Yet, the limits to viable hybrid genome formation are poorly understood. Here we investigated to what extent hybrid genomes are free to evolve by sequencing the genomes of four island populations of the homoploid hybrid Italian sparrow Passer italiae. We report that a variety of novel and fully functional hybrid genomic combinations are likely to have arisen independently on Crete, Corsica, Sicily and Malta, with differentiation in candidate genes for beak shape and plumage colour. However, certain genomic regions are invariably inherited from the same parent species, limiting variation. These regions are over-represented on the Z chromosome and harbour candidate incompatibility loci, including DNA-repair and mitonuclear genes. These gene classes may contribute to the general reduction of introgression on sex chromosomes. This study demonstrates that hybrid genomes may vary, and identifies new candidate reproductive isolation genes.
杂交是变异的重要来源；它跨越物种界限转移适应性遗传变异，并产生新的物种。然而，可行的杂种基因组形成的限制还知之甚少。在这里，我们通过对同源杂种意大利麻雀 Passer italiae 的四个岛屿种群的基因组进行测序，研究了杂种基因组在多大程度上可以自由进化。我们报告说，在克里特岛、科西嘉岛、西西里岛和马耳他岛，可能有多种新的和完全功能的杂种基因组组合独立出现，喙形和羽毛颜色的候选基因也存在分化。然而，某些基因组区域总是从同一亲种遗传下来，限制了变异。这些区域在 Z 染色体上的比例过高，并且包含候选的不兼容基因座，包括 DNA 修复和线粒体核基因。这些基因类可能有助于减少性染色体上的渐渗。这项研究表明，杂种基因组可能会发生变异，并确定了新的候选生殖隔离基因。
