椭圆叶花锚的花特征变异对交配系统和种群遗传多样性影响

Plant mating system could be affected by the variations of floral traits, and inbreeding depression and population genetic diversity might change correspondingly. However, it still remains unclear on the relatinships among floral traits, mating system and the population genetic diversity in alpine environments, where pollinator service is generally considered to be scarce. Halenia elliptica, a biennial with wide distribution in China, could produce seeds via both selfing and outcrossing, and a negative relationship was found between flower size and latitude in this plant, indicating the transition from outcrossing to selfing, which might be a good material to examine the relationships among floral traits, selfing rate, inbreeding depression and genetic diversity. In this proposal, based on wide collections of the leaves and seeds in different populations of H. elliptica along the latitudinal gradients, we will examine the selfing rate and the population genetic diversity. Moreover, we will examine the changes in floral character, expression of inbreeding depression in different stage of life history based on field experiments and common gardens. Our results in this proposal will discover the effects floral traits on mating system, inbreeding depression and genetic diversity on population level, and enhance our understanding on the reproductive stragety of short-lived alpine plants and maintenance of mixed mating system.

植物的花特征变化通常会影响植物的交配系统，进而可能会改变近交衰退和种群的遗传多样性，但在缺乏传粉者的高山环境中，植物的花特征与交配系统和种群遗传多样性的关系仍不明确。兼具自交和异交能力的两年生植物椭圆叶花锚的花大小随纬度升高表现出显著降低的趋势，表明随纬度升高椭圆叶花锚可能存在由异交向自交进化的趋势，为花特征、交配系统和种群遗传多样性的相互关系研究提供了一个理想的材料。本项目拟通过在纬度梯度上采集不同种群的叶片和种子，检测不同种群的自交率和遗传多样性，并通过野外实验和同质园实验揭示花特征进化的选择压力以及近交衰退在不同生活史阶段的表达。本项目的研究结果将在种群水平揭示植物花特征对交配系统、近交衰退和遗传多样性的影响，并能拓宽我们对高山短命植物繁殖策略和混合交配系统维持机制的理解。

本项目结合野外和室内实验研究了椭圆叶花锚的传粉生态学、花部特征变化和自交率。在三个种群开展了野外实验，证明椭圆叶花锚的交配系统类型为混合交配系统。基于转录组测序技术开发了椭圆叶花锚的SSR引物，并利用SSR引物检测了纬度梯度上7个种群的自交率，同时结合测量的距长度分析了自交率与距长度的相互关系以及16个种群的遗传多样性和遗传结构。研究结果表明，椭圆叶花锚距长度的变化与传粉者的选择压力关系不大，自交率随纬度升高不断增加，高纬度种群较高的近交衰退阻止了完全自交的进化并维持了该物种混合的交配系统；该物种表现出了中等偏下程度的遗传多样性，可能与该物种在高纬度自交为主的繁育系统导致了遗传多样性的降低有关，也可能表明该物种是向高纬度扩张，扩张的过程中经历了遗传漂变以及有效种群规模较小和等位基因流失而导致了遗传多样性得降低。本研究为椭圆叶花锚的交配系统进化与花部特征演化的相互关系提供了证据，为探讨椭圆叶花锚种群历史动态提供了前期基础。