报春花属植物交配系统转变研究

	报春花属植物交配系统转变研究
	钟莉
导师	王红
关键词	报春花属，交配系统，二型花柱，同型花柱，自交综合征，遗传多样性，性状演化 Primula, mating system, distyly, homostyly, genetic diversity, selfing syndrome, trait evolution
摘要	交配系统由异交向自交转变在被子植物演化中频繁发生。尽管如此，在自然界中，以自交为主的物种仅占被子植物的10-15%。Stebbins在1957年曾提出一个经典理论，他认为自交是生物进化的“死胡同”（dead end）。但是自交的物种在某些条件下也会受到自然选择的倾向。因为在自交过程中会存在繁殖保障效应（reproductive assurance）和自动传递优势（transmission advantage），在一定程度上能够抵消近交衰退导致的适合度的下降。本研究以兼具同型花柱和异型花柱物种的报春花属（Primula）为研究对象，利用异型花柱物种类群以异交的交配系统为主，而同型花柱物种以自交的交配系统为主的特点，对该属内交配方式差异明显的物种进行了系统发育基因组学、繁殖性状演化和种群群遗传学的综合研究，探讨其交配系统演化的方向及其潜在的遗传和生态效应。主要的结论包括：鄂报春组的10个物种的37个叶绿体全基因组系统发育重建结果表明鄂报春组为一个单系（BP = 100%，PP = 1）,包括两个主要的分支；性状重建结果表明花柱异型为该类群祖征，而花柱同型为衍征，同型花柱在鄂报春组内多次起源，其中至少发生了四次的独立演变。基于15个微卫星分子标记，我们进一步对鄂报春组10个物种40个居群（25个异型花柱居群和15个同型花柱居群）共600个个体开展群体遗传学分析。结果表明，衍生的同型花柱物种相对二型花柱祖先物种呈现出极高的自交率和极低的遗传多样性储备。当K = 17时，亚群的分群最为明确，同型花柱物种聚为5个不同的分支，居群遗传结构的分析印证了系统学的结果。为了探究不同花型的表型差异，我们统计了鄂报春组的964朵花（长柱花: n=219; 短柱花: n = 226; 同型花: n = 522）的花的形态特征差异，结果表明所有独立起源的同型花柱物种中均出现明显的自交综合征发育信号。同型花柱物种的花展示大小和花粉产量明显减低，但是花粉大小却大于异型花柱物种。报春花科四个属的110个物种（156个样品）的叶绿体全基因组系统发育关系表明：报春花属与独花报春属亲缘关系更近，两者组成的分支与点地梅属互为姐妹群关系；报春花属并非是一个单系，假报春属嵌套在其中。报春花属与点地梅属的分化时间在渐新世的32.51Mya（27.71-37.48 Mya，95%HPD），并在中新世7.49Mya（3.89-13.24 Mya，95%HPD）呈现快速辐射分化。15个同型花柱物种，6个兼具同型花柱和异型花柱的三态物种位于不同分支的末端节点，说明同型花柱在报春花属中经历多次独立起源，且至少发生了约21次由异型花柱向同型花柱的转变。统计了报春花属48个物种的1864朵花（长柱花: n=588; 短柱花: n = 608; 同型花: n = 668）的13个花部性状的差异，线性混合效应分析结果表明除了花萼宽度，同型花柱物种在其余12个性状都表现出不同程度的自交综合征的趋势，尤其表现在雌雄蕊空间隔离、花冠宽幅和花粉大小等几个性状上。自交物种与异交物种在花冠正面观的形状上并无显著差异，而侧面观形状具有显著分化，主要体现为花冠筒长度的差异。自交物种的花表型整合程度高于异交物种，且花被组织的整合程度最高。短柱花整合程度与同型花相近，结合花粉大小等证据，推测同型花柱是由短柱花演变而来。基于报春花属叶绿体基因组的系统发育关系，采用系统发育比较法对多个花性状演化模式进行探究，结果表明：除了雌雄蕊隔离程度，其余的12个花性状均检测到显著的系统发育信号。花萼宽度、花冠筒长度、花冠筒开口大小、胚珠数量这四个性状经系统发育回归分析，不同花型间的差异均不显著（P＞0.05），其他性状在花型间存在显著差异（P<0.001）。去除系统发育关系的干扰后，性状间的相关性程度无明显改变，说明系统发育关系影响不大。各性状间的关联大部分为正相关，只有花粉大小与其他性状为负相关。十三个花部性状遵循着不同的演化模型，自交物种的性状最优值θ均小于或等于异交物种。综合上述结果表明，报春花属植物表型的演化受到了定向选择，衍生的同型花柱物种整体表现出花展示缩小以及雄性资源分配比例下降等典型的自交综合征。; The evolution of highly autogamous from obligate outcrossing is recognized as the most frequent reproductive transition in flowering plants. However, only ~10-15% of angiosperm species are predominant selfing particularly in herbaceous taxa. Stebbins (1957) initially proposed a classical theory for the evolutionary fate of selfing lineage as an “evolutionary dead end”. Selfing lineages are expected to arise frequently from outcrossing ancestors because of the transmission advantage of mating system modifiers and reproductive assurance under pollinator and/or mate limited conditions. Selfer will be favored if the benefit of autogamous offsets the impact of inbreeding depression. Homostylous plants most possess high selfing rates while distylous species are commonly obligate outcrossing due to heteromorphic incompatibility. Primula (Primulaceae), which has multiple distylous and homostylous taxa, provides a valuable comparative system for investigating the evolutionary consequences of mating system from outcrossing to selfing. By employing phylogenomics and population genetics approaches, the study explored the ecological and genetic consequences of mating system transition accompanies the evolutionary breakdown of heterostyly. The main results and conclusions are shown as below: We investigated the process of mating system transition in 37 samples representing 10 species of Primula section Obconicolisteri using phylogenomic approaches and character evolution. Section Obconicolisteri was strongly supported as monophyletic (ML bootstrap value: ML = 100%; Bayesian posterior: PP = 1.00) and two main clades were recovered both with strong nodal support. We suggest that the distyly has broken down to homostyly on multiple (at least four) occasions within the section. To further investigate mating patterns and genetic diversity of the species with contrasting mating system, 15 microsatellite loci were used to perform population genetics analysis in 40 populations (25 distylous, and 15 homostylous). Distylous populations were largely outcrossing whereas homostylous populations were characterised by high selfing rates. The estimates of genetic diversity in populations showed that homostylous populations exhibited substantially lower levels than distylous populations in allelic richness and heterozygosity. The best-fit K value was 17, and homostylous taxa were strongly supported as five clusters consistent with the prediction of multiple origins of homostyly. To test the floral morphological differentiation between homostyles and their distylous ancestors, we measured 967 flowers (L-morph: n = 219; S-morph: n = 226; H-morph: n = 522) randomly from 31 populations. All homostylous species exhibited the development of selfing syndrome to some extent. Flower size and pollen production were decreased in homostylous populations, but pollen size was significantly increased. Obconicolisteri is likely to have been fostered by the complex montane environments that sp
语种	中文
	2022-12
学位授予单位	中国科学院大学
文献类型	学位论文
条目标识符	http://ir.kib.ac.cn/handle/151853/75086
专题	昆明植物所硕博研究生毕业学位论文
推荐引用方式 GB/T 7714	钟莉. 报春花属植物交配系统转变研究[D]. 中国科学院大学,2022.

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