Genetic variation, cytotype associations and geographical parthenogenesis in the subtropical grass genus Paspalum

多倍性是开花植物进化过程中最重要的自发因素之一，它通过基因组复制和基因库碎片化促进了植物的多样化。在多倍体复合体中，它们的生殖模式和授粉综合征的特征决定了遗传变异和群体结构。另一方面，众所周知，杂交和多倍体化会造成与生殖系统变化相关的基因组震荡，如自育（自交配）或无融合（无性形成的种子）。育种系统的性状转变特别有趣，因为它们影响物种内遗传变异的数量和分布。此外，在传粉者或交配伙伴有限的情况下，自育和无融合生殖都是促进单代繁殖和增强殖民能力的机制（贝克定律）。通过自交受精和/或无融合生殖的生殖保证可以促进范围扩大，概述了地理细胞型多样性模式（如地理孤雌生殖），然而，生殖保证的好处可能被种子折扣、遗传多样性丧失和自交者的近交抑制所抵消。无融合生殖的其他潜在好处是生态位的划分和广泛克隆对资源空间的利用（冰冻生态位变异模型）或具有广泛生态能力的克隆的定殖能力（通用基因型）。为了研究决定自然种群地理分布和细胞型关联的复杂动力学，我们将利用雀稗（即雀稗）模型系统的优势。性自育/自育二倍体、性自育/自育四倍体、无杂种自育四倍体)的存在，并分析自交与异体、二倍体与多倍体、性与无杂种状态特征对群体水平上遗传变异和细胞型多样性的影响。利用流式细胞术研究倍性水平和发育途径。将利用扩增片段长度多态性和微卫星标记评估群体内部和群体之间的遗传变异和结构。不同细胞类型/生殖系统的比较将有助于了解这些因素对植物进化和生物地理学的重要性。

Polyploidy in flowering plants is one of the most significant spontaneous factors of evolutionary processes, promoting diversification via genome duplication and gene pool fragmentation. In polyploid complexes, the features of their reproductive modes, and pollination syndromes shape genetic variation and population structure. On the other hand, it is widely known that hybridization and polyploidization create a situation of genomic shock linked to changes in reproductive systems such as self-fertility (autogamy) or apomixis (asexually formed seeds). Breeding system character transitions are of particular interest because they affect the amount and distribution of genetic variation within species. Moreover, both self-fertility and apomixis are mechanisms that facilitate uniparental reproduction and enhance colonizing abilities where pollinators or partners for mating are limited (Baker's law). Reproductive assurance through self-fertilization and/or apomixis can promote range expansion outlining geographical cytotype diversity patterns (e.g. geographical parthenogenesis), however the benefit of reproductive assurance might be outweighed by seed discounting, loss of genetic diversity and in selfers, inbreeding depression. Other potential benefits to apomictic reproduction are partitioning of ecological niches and use of the resource space by broad arrays of clones (The Frozen Niche Variation Model) or the colonizing ability of clones with a broad ecological capacity (General Purpose Genotypes). To investigate the complex dynamics determining geographic distributions and cytotype associations in natural populations, we will take advantages of the model system Paspalum (ie. presence of sexual self-sterile / self-fertile diploids, sexual self-sterile / self-fertile tetraploids, apomictic self-fertile tetraploids), and analyse consequences of autogamy vs. allogamy, diploid vs. polyploid, sexual vs. apomictic state characters on genetic variation and cytotype diversity at population level. Ploidy levels and developmental pathways will be studied using flow cytometry. Genetic variation and structuring within and among populations will be assessed using Amplified Fragment Length Polymorphisms and microsatellite markers. The comparison of different cytotypes / reproductive systems will give insights into the importance of these factors for plant evolution and biogeography.