异型-同型花柱过渡相种群交配格局特征及其对性系统演替过程的启示

The feature of mating patterns in transitional population is of great significance for understanding the succession process of floral characters in the way of microevolutionary trajectory. As part of the floral syndrome, fitness difference between floral morphs can be reflected in the mating process, and therefore the sexual polymorphism is more like to undergo rapid and intense direntional selection resulting morphological transition. The group containning transition phase polymorphism provides an unsual opportunity to address several questions of general relevance to the breakdown of heterostyly to homostyly, since the transition phase of phenotypic population was ephemeral in the evolutionary time scale. . Primula chungensis is of particular interest because it is a species with both distylous and homostylous populations and even the trimorphic populations in which all three morphs coexist. This species therefore provides a rare example of the replacement of sexual polymorphism by floral monomorphism in a heterostylous species. By investigating mating patterns of artificial populations with different floral morph ratios inferred from paternity analysis, we address the following questions: First, what are the most important factors that determine the initial progress of newly occurring homostyles? Second, to what extent are the morph ratio and pollinator environment important for patterns of mating in transitional population? Finally, we aim to determine whether the transition of mating system from out crossing to selfing accounts for the dynamic of species diversity in a particular distylous-homostylous taxa. This project will provide novel insights into how and why distyly breaks down to homostyly and the ecological and genetic consequences of this transition. In addition the sexual polymorphic component of the study will provide valuable information on the role of ecological and genetic factors influencing the origin and maintenance of primula species in Himalaya-Hengduan Mountains Region.

作为微进化现象的一个缩影，过渡相种群交配网络格局特征对于理解物种性状演替过程具有重要意义。构成花部综合征的繁殖性状在表型间的适合度差异能够在过渡相种群内的交配环节中获得体现，它使得多态的性表型受到快速而强烈的定向选择作用而表现为花型转变现象。在进化的时间尺度上，性表型相关的过渡相种群可谓转瞬即逝，因此少数包含性状过渡相特征的表型多态类群是开展性状演替研究的理想素材。本项目选用中甸灯台报春，利用该物种具备二型花柱向同型花柱转变的典型特征；通过构建一系列性比的人工种群和父本推断的方法，重点围绕性状演替的内部生理遗传因素、外部生态环境促成条件，以及在进化时间尺度上性系统转变与类群盛衰的关系等三方面问题，开展进化生态学研究。项目的实施有望为异型与同型花柱之间的演化转变提供新的证据；同时，从植物性系统演替与分化的层面上加深理解喜马拉雅-横断山区报春花属及其相关类群的物种多样性发生与维持机制。

作为微进化现象的一个缩影，过渡相种群交配网络格局特征对于理解物种性状演替过程具有重要意义。构成花部综合征的繁殖性状在表型间的适合度差异能够在过渡相种群内的交配环节中获得体现，它使得多态的性表型受到快速而强烈的定向选择作用而表现为花型转变现象。在进化的时间尺度上，性表型相关的过渡相种群可谓转瞬即逝，因此少数包含性状过渡相特征的表型多态类群是开展性状演替研究的理想素材。本项目选用中甸灯台报春，利用该物种具备二型花柱向同型花柱转变的典型特征；通过构建一系列性比的人工种群和父本推断的方法，重点围绕性状演替的内部生理遗传因素、外部生态环境促成条件，以及在进化时间尺度上性系统转变与类群盛衰的关系等三方面问题，开展进化生态学研究。研究结果表明：1）群体内的性比结构是影响性系统转变的最重要因素，尤其是当同型花柱个体比例达到一定程度之后，花型决定基因会通过自交的形式在群体内部爆发式增长；2）长柱花和短柱花个体之间的雄配子体竞争力没有明显差异，同型花个体的雄配子体竞争力略弱与异型花个体，因此，从花粉管竞生的生理角度来看，雄配子体竞争力在一定程度上抑制同型花决定基因在群体内部的扩展；3）三种花型均存在一定程度的隐存自交不亲和性，且同型花的自交不亲和性相对最强，因此，同型花的亲和性特征也在一定程度上抑制同型花决定基因的扩展。本项目的研究表明，同型花柱的繁殖生态特征对表型比例增长起促进作用，而配子体竞生和隐存亲和性特征对花型比例增长起抑制作用。