报春花属植物交配系统转变的遗传效应

	报春花属植物交配系统转变的遗传效应; The genetic consequences of mating system transition in genus Primula L.
	王昕嘉
导师	王红
摘要	The transition from outcrossing to self-fertilization is considered the most common evolutionary transition in flowering plants. Selfing species evolved repeatedly in many independent lineages but were rarely long-lived. Selfing lineages suffer from an increased risk of extinction owing to a reduced potential for adaption, only 10-15% of seed plants are predominantly selfing. Accordingly, the evolutionary transition from outcrossing to selfing can have important genomic consequences. Compared to outcrossing, selfing species reduces effective population size, heterozygosity, effective recombination, genetic diversity and efficacy of selection. As a consequences, selfing species are expected to show significant patterns of molecular evolution, genomic degradation and low adaption potential. The “genomic selfing syndrome” has been proposed recently to summarize the genetic effects accompanies mating-system transitions. Despite the theoretical expectation of genomic degradation under recurrent selfing, empirical evidence for selfing as an “evolutionary dead end” is mixed. Here, we employ phylogenetically informed comparative approaches of protein-coding genes to investigate the genetic and genomic consequences of mating-system transitions in a sample of 66 species of distylous and homostylous Primula. In the case of homostylous species, the transition to high selfing rates is usually through the evolutionary breakdown of heterostyly to homostyly. In contrast to the relatively gradual evolution of selfing rates via mixed mating, characteristic of most mating-system transitions in angiosperms, predominant selfing arises very rapidly in distylous taxa, by genetic changes at the S locus linkage group governing heterostyly. Our sampling of homostyles provides a novel opportunity to evaluate genomic selfing syndrome of different time scales of mating-system transitions in a system in which homostyles are derived repeatedly in different lineages. We conducted a macroevolutionary investigation between homostylous and distylous Primula with their contrasting mating-system. We complemented our comparative analysis with a microevolutionary study of P. chungensis, which comprised distylous and homstylous populations. We generated molecular evolutionary analysis of sequence divergence and polymorphism data based on both choloplastic and nuclear genomic datasets. The main results are summarized as follows: (1) In macroevolutionary comparison, homostylous species exhibited reduced heterozygosity and efficacy of purifying selection, and an accelerated accumulation of slightly deleterious mutations Using both chloroplast and nuclear coding sequences, we found significantly higher nonsynonymous versus synonymous divergence ratios (dN/dS) in homostylous than distylous species. The analysis results based on the concatenated datasets were concordant with results based on individual gene alignments. Meanwhile, the possibility that higher dN/dS in “evolving differentially”
	2020-11
文献类型	学位论文
条目标识符	http://ir.kib.ac.cn/handle/151853/74236
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	王昕嘉. 报春花属植物交配系统转变的遗传效应, The genetic consequences of mating system transition in genus Primula L.[D],2020.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
王昕嘉-王昕嘉毕业论文_终版35656b（5349KB）	学位论文		限制开放	CC BY-NC-SA	请求全文