Dissertation Research: Agmatoploid Chromosome Number Change and Speciation: Molecular Phylogenetic and Cytogenetic Studies in Carex Section Acrocystis

[801495]长期以来，染色体变化在物种形成中的重要性及其在产生生殖障碍中的作用被认为是导致形态多样化的一个因素。Carex L. （Cyperaceae）是研究染色体变化过程的理想系统，它是世界上已知的最大的属之一，大约有2000种，染色体数目从n=6到68不等。本研究将探讨三个问题：1)染色体数目的变化在毛苔属物种形成中起什么作用；2)毛苔属Acrocystis组内物种间的细胞遗传学变化涉及什么机制；3)毛苔属Acrocystis组内世系间的关系以及Acrocystis组与毛苔属其他组间的关系。两个细胞核和一个叶绿体DNA区域的分子系统发育分析将用于创建一个框架，用于研究染色体变化模式，该模式使用染色体计数，流式细胞术测量基因组大小，具有不同染色体数的物种之间的生育能力以及染色体上重复DNA元件（如端粒）的位置。这四种不同的数据集，连同系统发育假说，将被用来指示染色体变化的种类和变化发生的方向。

9801495 Columbus The importance of chromosomal change in speciation and its role in producing reproductive barriers has long been recognized as a factor that can lead to morphological diversification. An ideal system with which to study processes of chromosome change is Carex L. (Cyperaceae) one of the largest genera in the world with approximately 2,000 species recognized, which has an extremely wide range of chromosome numbers from n=6 to 68. Three questions will be investigated in this study: 1) What role does change in chromosome number play in speciation in Carex. 2) What mechanisms are involved in cytogenetic change among species within Carex section Acrocystis. 3) What are the relationships among lineages within section Acrocystis and between Acrocystis and other sections of Carex? Molecular phylogenetic analyses of two nuclear and one chloroplast DNA region will be used to create a framework for studying the patterns of chromosomal change measured using chromosome counts, flow cytometric measurements of genome size, fertility among species with different chromosome numbers, and position of repetitive DNA elements such as telomeres on the chromosomes. These four different data sets, together with phylogenetic hypotheses, will be used to indicate both the kinds of chromosomal change and the direction that change has occurred.