Yang Jie, Fu Weirui, Xu Haoming, Song Zhiping, Zhang Wenju, Yang Ji, Wang Yuguo
Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China.
Front Genet. 2020 Feb 4;10:1250. doi: 10.3389/fgene.2019.01250. eCollection 2019.
Hybrid speciation is an important way to generate species diversity. In general, however, interspecific hybridization is easily confused with the formation of hybrid species. Using the genomic resequencing data of the kiwifruit genus (), at least ten species were documented recently as homoploid hybrid species, and thus a two-layer mode of species diversification has been proposed. As a crucial piece of evidence, was identified as a hybrid derivative of × , representing a rare case of hybrid species in kiwifruit that won the competition of ecological niches with one of its putative parental species, . However, the hypothesized hybrid origin of is inconsistent with our specimen observations. Here, we present multiple lines of evidence to reject the hybrid speciation hypothesis for this species, despite genomic evidence for frequent interspecific gene flow. We collected the samples of in type locality and neighboring regions to contrast them with type specimen, and sequenced nuclear ribosomal DNA ITS, chloroplast L-F and mitochondrial , as well as four single-copy nuclear genes explored from kiwifruit genomes, to infer phylogenetic relationships among , its putative parental species, and their relatives. Our data definitely reveal that occupies an independent backbone lineage and it is not a hybrid. This study suggests that correct evolutionary applications on extensive surveys of the putative hybrid and its possible parents with strict criteria are necessary in the documentation of hybrid speciation to advance our understanding of the genomic basis of hybrid species.
杂交物种形成是产生物种多样性的重要方式。然而，一般来说，种间杂交很容易与杂交物种的形成相混淆。利用猕猴桃属的基因组重测序数据，最近记录了至少10个物种为同倍体杂交物种，因此提出了一种两层模式的物种多样化。作为关键证据，[物种名称]被确定为[亲本物种1]×[亲本物种2]的杂交衍生物，这代表了猕猴桃中杂交物种的一个罕见案例，即它与其假定亲本物种之一[亲本物种1]竞争生态位并获胜。然而，[物种名称]假定的杂交起源与我们的标本观察结果不一致。在这里，尽管有基因组证据表明存在频繁的种间基因流动，但我们提供了多条证据来反驳该物种的杂交物种形成假说。我们在模式产地和邻近地区采集了[物种名称]的样本，将它们与模式标本进行对比，并对核糖体DNA ITS、叶绿体L-F和线粒体[基因名称]进行测序，以及对从猕猴桃基因组中发掘的四个单拷贝核基因进行测序，以推断[物种名称]、其假定亲本物种及其近缘种之间的系统发育关系。我们的数据明确表明，[物种名称]占据一个独立的主干谱系，它不是杂交种。这项研究表明，在记录杂交物种形成时，对假定的杂交种及其可能的亲本进行广泛调查并采用严格标准进行正确的进化应用，对于推进我们对杂交物种基因组基础的理解是必要的。
