Hybridization can drive speciation. We examine the hypothesis that Castanea henryi var. omeiensis is an evolutionary lineage that originated from hybridization between two near-sympatric diploid taxa, C. henryi var. henryi and C. mollissima. We produce a high-quality genome assembly for mollissima and characterize evolutionary relationships among related chestnut taxa. Our results show that C. henryi var. omeiensis has a mosaic genome but has accumulated divergence in all 12 chromosomes. We observe positive correlation between admixture proportions and recombination rates across the genome. Candidate barrier genomic regions, which isolate var. henryi and mollissima, are re-assorted in the hybrid lineage. We further find that the putative barrier segments concentrate in genomic regions with less recombination, suggesting that interaction between natural selection and recombination shapes the evolution of hybrid genomes during hybrid speciation. This study highlights that reassortment of parental barriers is an important mechanism in generating biodiversity.

杂交可以驱动物种形成。我们研究了锥栗（Castanea henryi var）的假说。omeiensis是一种进化谱系，起源于两个近交二倍体类群C. henryi var之间的杂交。亨利和C. mollissima。我们为mollissima生产高质量的基因组装配，并描述相关板栗类群之间的进化关系。我们的结果表明，C。henryi var。峨i有一个镶嵌基因组，但在所有12条染色体上都积累了发散。我们观察到整个基因组中混合比例和重组率之间存在正相关。隔离var的候选障碍基因组区域。henryi和mollissima在杂种谱系中重新分类。我们进一步发现推定的障碍片段集中在重组较少的基因组区域，这表明自然选择和重组之间的相互作用塑造了杂种形成过程中杂种基因组的进化。这项研究强调了父母障碍的重排是产生生物多样性的重要机制。