Abstract：
Despite the importance of hybridization in evolution, the evolutionary consequence of homoploid hybridizations in plants remains poorly understood. Specially, homoploid hybridization events have been rarely documented due to a lack of genomic resources and methodological limitations. Actinidia zhejiangensis was suspected to have arisen from hybridization of Actinidia eriantha and Actinidia hemsleyana or Actinidia rufa. However, this species was very rare in nature and exhibited sympatric distribution with its potential parent species, which implied it might be a spontaneous hybrid of ongoing homoploid hybridization. Here, we illustrate the dead-end homoploid hybridization and genomic basis of isolating barriers between A. eriantha and A. hemsleyana through whole genome sequencing and population genomic analyses. Chromosome-scale genome assemblies of A. zhejiangensis and A. hemsleyana were generated. The chromosomes of A. zhejiangensis are confidently assigned to the two haplomes, and one of them originates from A. eriantha and the other originates from A. hemsleyana. Whole genome resequencing data reveal that A. zhejiangensis are mainly F1 hybrids of A. hemsleyana and A. eriantha and gene flow initiated about 0.98 million years ago, implying both strong genetic barriers and ongoing hybridization between these two deeply divergent kiwifruit species. Five inversions containing genes involved in pollen germination and pollen tube growth might account for the fertility breakdown of hybrids between A. hemsleyana and A. eriantha. Despite its distinct morphological traits and long recurrent hybrid origination, A. zhejiangensis does not initiate speciation. Collectively, our study provides new insights into homoploid hybridization in plants and provides genomic resources for evolutionary and functional genomic studies of kiwifruit.
摘要：
尽管杂交在进化中很重要,植物中同倍体杂交的进化结果仍然知之甚少。特别是,由于缺乏基因组资源和方法上的限制，很少记录同倍体杂交事件。怀疑浙江猕猴桃是由A.eriantha和A.hemsleyana或A.rufa的杂交产生的。然而,该物种在自然界中非常罕见，并与其潜在的亲本物种表现出同胞分布，这暗示它可能是正在进行的同倍体杂交的自发杂种。这里,我们通过全基因组测序和群体基因组分析说明了死端同倍体杂交和分离A.eriantha和A.hemsleyana之间屏障的基因组基础。产生了zhejiangensis和a.hemsleyana的染色体规模基因组组装体。浙江曲霉的染色体被自信地分配给两个单倍体，它们都来自A.eriantha和A.hemsleyana,分别。全基因组重测序数据显示，浙江A.主要是A.hemsleyana和A.eriantha的F1杂种，基因流始于约98万年前，这意味着这两种截然不同的猕猴桃之间既有强大的遗传障碍，也有正在进行的杂交。包含与花粉萌发和花粉管生长有关的基因的五个倒位可能是A.hemsleyana和A.eriantha之间杂种的育性破坏的原因。尽管其独特的形态特征和长期反复出现的杂种起源，A.浙江不启动物种形成。总的来说，我们的研究为植物中的同倍体杂交提供了新的见解，并为猕猴桃的进化和功能基因组研究提供了基因组资源。
