DISSERTATION RESEARCH: Untangling the Cystopteris fragilis Complex: An Investigation of the Effects of Polyploidy on Diversification Rates

可以说，最引人注目的突变（全基因组复制或多倍体）会导致个体的染色体数量是其父母的两倍。多倍体在植物中是一种常见且持续存在的现象，例如许多作物都是多倍体。本项目旨在研究蕨类植物多倍体谱系的进化潜力和命运，几乎所有物种在其进化历史中都经历过一次或多次多倍体。全球分布的蕨类植物Cystopteris包含了二倍体和多倍体的复杂组合，使其成为研究多倍体对多样化率影响的理想选择。利用200个Cystopteris个体的DNA序列数据，每个已知的倍性水平，将推断进化关系，重建祖先的倍性水平，并估计物种形成和灭绝率。尽管多倍体的普遍性和科学重要性，多倍体的长期潜力和进化动力学仍然存在争议——多倍体谱系是容易迅速灭绝的“死胡同”，还是它们反而推动了进化的新颖性？这一实证研究为理解多倍体的进化重要性做出了重要贡献，对进化理论、生物多样性保护和作物改良具有重要意义。

Arguably the most dramatic mutation possible (whole-genome duplication, or polyploidy) results in an individual with double the chromosome number of its parents. Polyploidy is a common and ongoing phenomenon in plants, where many crops, for example, are polyploid. This project aims to examine the evolutionary potential and fate of polyploid lineages in ferns¬¬a plant group where nearly all species have experienced one or more episodes of polyploidy in their evolutionary past. The globally distributed fern genus Cystopteris encompasses a complex mix of diploid and polyploid species, making it ideal for investigating the effects of polyploidy on diversification rates. Using DNA sequence data from 200 Cystopteris individuals, each of known ploidy level, evolutionary relationships will be inferred, ancestral ploidy levels will be reconstructed, and speciation and extinction rates will be estimated through time. Despite its ubiquity and scientific importance, the long-term potential and evolutionary dynamics of polyploidy remain contentious--are polyploid lineages "dead-ends" that are prone to rapid extinction, or do they instead drive evolutionary novelty? This empirical study is well positioned to make a key contribution to understanding the evolutionary importance of polyploidy, with implications for evolutionary theory, biodiversity conservation, and crop improvement.