The role of hybridization and polyploidy in plant evolution

杂交（物种间的杂交）和多倍体（染色体加倍）是显花植物中普遍存在的现象。它们共同导致新的性状组合，这些性状可以稳定为新的异源多倍体物种，对植物进化产生根本性影响。这通常具有实际重要性，例如在评估稀有物种的分类地位或作物与相关杂草杂交的后果时。因此，了解多倍体杂种是如何产生和进化的是很重要的。这项工作的重点是杂交的重要性，在两个不同的植物群体，小鹿百合（Erythronium）和北美紫苑（Symphyotrichum）。进化关系在这些群体中得到很好的理解，使得杂交种很容易使用分子工具检测。该项目利用来自特定叶绿体和核基因区域的DNA序列数据，这些数据提供了关系的精细尺度分辨率。它有几个组成部分：（1）系统发育分析和检测这些类群中的杂交（特别是导致多倍体杂种的杂交）;（2）确定杂种频率和亲子关系;（3）研究异源多倍体的遗传特征，包括重复基因的变化，通过比较天然异源多倍体物种与它们的亲本物种，以及通过从相同亲本合成人工杂种。这项工作将提高对植物中新的遗传形式产生和维持的方式的理解。

Hybridization (interbreeding of species) and polyploidy (chromosome doubling) are widespread phenomena in the flowering plants. Together they lead to new combinations of traits that can become stabilized as new allopolyploid species, with fundamental consequences for plant evolution. This is often of practical importance, for example when assessing the taxonomic status of rare species or the consequences of interbreeding between crop plants and related weeds. It is therefore important to understand how polyploid hybrids arise and evolve. This work focuses on the importance of hybridization in two distinct plant groups, fawn-lilies (Erythronium) and North American asters (Symphyotrichum). Evolutionary relationships are well understood in these groups, allowing hybrids to be readily detected using molecular tools. This project makes use of DNA sequence data from specific chloroplast and nuclear gene regions that give fine-scale resolution of relationships. It has several components: (1) phylogenetic analyses and detection of hybridization (especially leading to polyploid hybrids) in these groups; (2) determination of hybrid frequency and parentage; and (3) investigation of the genetic characteristics of allopolyploids, including changes in duplicated genes, by comparison of natural allopolyploid species with their parent species and by synthesis of artificial hybrids from the same parents. This work will enhance understanding of the ways in which new genetic forms are created and maintained in plants.