RUI: Tree Fern Phylogeny and Evolution: Molecular EvidenceFrom Two Genomes

9307211 Stein和Conant世界上的桫椤，属于桫椤科，是蕨类植物的一大类群，约有500种，染色体数目变化不大。在蕨类植物中，多倍体（染色体补体加倍）和异倍体（单个染色体对的增加或减少）标志着许多谱系。在树蕨中可能存在新的物种分化机制，如杂交后的二倍体水平的物种形成。然而，为了探索这种机制，需要树蕨的系统发育框架，以便合理选择目标或代表性物种进行分析。Drs。斯坦和科南特正在继续他们对树蕨的系统发育分析，现在集中在来自澳大利亚地区的旧大陆物种上。他们正在分析叶绿体和核基因的DNA突变，以获得新的分子数据，用于系统发育重建，并与蕨类植物分类的传统形态特征相结合。来自基因测序的新分子数据正在彻底改变我们对生物进化关系的理解。对旧大陆蕨类植物的研究将在传统形态特征的基础上增加叶绿体和核基因的数据，以增强对新世界蕨类植物的研究。这一大型植物群的强大系统发育将有助于集中研究新的物种形成机制，并进一步分析这些蕨类植物解剖和生态特征的变化方向。

9307211 Stein and Conant The tree ferns of the world, placed in the family Cyatheaceae, are a large group of ferns, ca. 500 species, with little variation in chromosome number. In this they are unusual for ferns, where polyploidy (chromosome complement doubling) and dysploidy (increase or decrease of individual chromosome pairs) mark many lineages. Possibly novel mechanisms of species divergence may operate in the tree ferns, such as diploid level speciation after hybridization. To explore such mechanisms, however, a phylogenetic framework for the tree ferns is required, in order to rationalize the choice of target or representative species for analysis. Drs. Stein and Conant are continuing their phylogenetic analyses of tree ferns, concentrating now on Old World species from the australasian regions. They are analyzing DNA mutations in chloroplast and nuclear genes to acquire new molecular data for phylogenetic reconstruction and to integrate with traditional morphological characters from fern taxonomy. %%% New molecular data from gene sequencing are revolutionizing our understanding of the evolutionary relationships of organisms. Work on Old World tree ferns will add data from both chloroplast and nuclear genes to traditional morphological features, to augment work on New World tree ferns. A robust phylogeny for this large group of plants will allow focused study on novel mechanisms of speciation and further analysis of t he direction of change in anatomical and ecological features of these ferns.