Phylogeny of Skeletonema (Bacillariophyceae)

这项研究将在分支系统学框架下使用分子和形态计量学方法对海洋硅藻属骨架藻的系统发育进行严格的推断。在较低的系统发育水平上，该属可作为探索主要无性生物系统发育重建的方法和争议的模式系统。将探讨以下问题：1.利用叶绿体DNA(CpDNA)、核rDNA和单拷贝基因nucDNA基因测量种群和物种之间的差异水平；2.基因树和物种树在较低系统发育水平上的关系；3.用系统发育系统方法分析分子和形态数据的一致性。据推测，该属最原始的成员是高光、低营养的温暖海洋环境特有的高度硅化的形式，而最衍生的成员是生活在浑浊、富营养化的温带淡水和微咸水环境中的轻度硅化的形式。骨骼线虫的生态重要性和丰富的背景数据使其成为在历史背景下检验适应假说的理想系统。

This study will result in rigorous inferences of phylogeny for the marine diatom genus Skeletonema using molecular and morphometric methods in a cladistic framework. It is proposed that this genus can serve as a model system for exploring methods and controversies in the phylogeny reconstruction of primarily asexual organisms at lower phylogenetic levels. The following issues will be explored: 1. Levels of divergence among populations and species measured using chloroplast DNA (cpDNA), nuclear rDNA, and a single copy gene nucDNA gene; 2. Relationships of gene trees and species trees at lower phylogenetic levels; 3. Concordance of molecular and morphological data analyzed using phylogenetic systematic methods. It is hypothesized that the most primitive members of the genus are heavily silicified forms endemic to high-light, oligotrophic warm marine environments and that the most derived members are lightly silicified forms inhabiting turbid, eutrophic temperate freshwater and brackish water environments. The ecological importance and the wealth of background data available for Skeletonema make it an ideal system in which to test hypotheses of adaptation in an historical context.