岷江百合 Lilium regale Wilson及近缘类群生态物种形成机制研究

The delimitation and discrimination of species boundaries is one of the most important questions that confound taxonomists in botany. The recognition of species notion will promote the understanding of formation and persisting of biodiversity. In recent, the ecological factors were found contributed more and more significant in speciation process, yet the mechanism that how species reacted to ecological pressures is seldom studied. Previous research on the genus Lilium of the author recovered a monophyletic clade named Leucolirion distributed over up and middle Yangtze River which included six species have very closed molecular affinity, however, varied a lot on the morphology and can divided easily into two types by flower. These two flower types are proved to be directly related to the pollinator preferences. This is a typical pattern of ecological induced speciation. In this study, we use this endemic monophyletic group as model to do such researches as 1) clarify its population genetic structure and excluded the affections might be caused by hybridization and introgression; 2) use full-length transcriptome method to make references and then compare the differences of these six species with transcriptome data, which is hope to recover the genetic bases of flower morphology variation. This program are aimed to answer these questions as 1) the species mechanism and distribution pattern of the up and middle Yangtze River, and 2) using this endemic group as model to try to discover the mechanism of speciation on the genome level and provide a new case study on species boundary and species delimitation.

物种界限的界定与划分一直是困扰分类学的重要问题之一。对物种概念的理解有助于更好的理解生物多样性的形成和维持。生态因素在物种形成研究中的作用越来越显著，但是物种自身响应生态选择压力的机制研究却很少。申请者前期研究发现百合属中一个我国特有的岷江百合单系分支包含的6个物种有很近的遗传距离却在形态上区别显著。而这样的差异和传粉者的选择直接相关，是典型的生态诱导物种分化形成新物种的实例。本项目拟在澄清群体遗传结构、排除杂交及基因渐渗的干扰基础上，采用全长转录组作为参照，对这个特有的类群6个物种的转录基因组进行比较研究，进而阐明与花部结构变化相关的分子机制。本研究的主要目的包括：1）对岷江百合等6种百合属姊妹类群的分布式样、群体遗传结构进行解析，揭示长江中上游地区物种分化模式；2）以该类群为例，对快速物种形成的分子机制在基因组水平上进行解析和揭示，并为物种形成和物种界限研究提供新的实例。

本研究通过对百合属岷江百合分枝的研究，采用高通量测序、群体遗传学的时段，并结合生态物种形成理论，对该分支的物种分化形成进行了研究。通过转录组数据和叶绿体基因组数据对6个物种的系统发育关系的重建可以得出，高通量数据在物种界限的界定方面非常有效，可以揭示或者进一步厘清物种间的关系，比单一运用少量片段更准确。岷江百合分枝的关系符合预期，按照花部结构分为两枝，它们互为姊妹类群。其中喇叭花状的分枝中岷江百合最为原始；剩余三个物种分布较广，虽然存在一定的基因流，但有明显的物种界限，且地域之间的变异较为稳定。反卷花部类型的两个物种，虽然同域分布，但是由于占领完全不同的生境，导致花期的隔离，基因交流非常有限。通过对比传粉学研究可以发现，喇叭花状分枝和反卷类型的传粉者截然不同，分别为夜间传粉的天蛾类和白天传粉的凤蝶类。完全不同的花部类型导致喇叭状花和反卷状花类群之间隔离显著，完全不存在基因交流。而反卷类型虽共享传粉者，由于二者花期的隔离效应，物种界限维持的很好。喇叭状类型中，虽然共享一类传粉者，其遗传结构受到花期（岷江百合最早开放）、花管长度影响（岷江百合花管最短）呈现出不同的遗传距离差异和基因交流模式。所有这些因素的叠加，造成了我们现在能观测到的物种的格局和遗传结构。本研究表明，物种的形成和维持是一个长期、连续的过程，物种的形成也是动态的连续过程。物种界限的维持和隔离的机制和效果直接相关。