Phylogenetic Relationships of Dennstaedtioid Ferns Based on DNA Sequence Analysis

9307091沃尔夫确定生物之间的进化关系是系统学家的一个主要目标；系统发育学为研究进化过程、生物地理扩散和迁徙以及与共生体和其他生态伙伴的共同进化提供了必要的历史框架。近年来，DNA测序为植物，特别是开花植物的系统发育分析提供了有价值的新数据。在历史上，蕨类植物一直是主要的分类混乱的主题，特别是在较高的分类级别(科和目)，这一组约10,000种存在着各种各样的分类和假设的系统发育。这种混淆的部分原因是缺乏形态特征，这些特征在表达上或从物种到物种都是可变的，但足够连贯，足以同源，即在许多不同的物种和属之间相似和可比较。由于这两个原因，DNA序列数据是理想的特征：在分类群中可变，但在所有分类群中具有可比性，至少在功能上重要的基因上是如此。犹他州州立大学的保罗·沃尔夫博士正在对许多蕨类植物的叶绿体光合作用基因进行DNA测序，以便在突变差异跟踪物种随时间的差异的工作假设下重建它们的系统发育。一组独立的分子数据将为评估不同蕨类的起源以及检查形态和染色体变异模式提供有价值的工具。蕨类蕨类植物是细孢子蕨类植物的主要组成部分，这项研究的数据最终将与其他致力于蕨类植物DNA测序的实验室的结果相结合，为所有主要的蕨类植物谱系提供一个系统发育框架。

9307091 Wolf Determining evolutionary relationships among organisms is a major goal of systematists; phylogenies provide the necessary historical framework for studies of evolutionary processes, biogeographic dispersal and migration, and coevolution with symbionts and other ecological associates. Recently, DNA sequencing has provided valuable new data for phylogenetic analysis of plants, especially the flowering plants. Historically, ferns have been the subject of major taxonomic confusion, particularly at upper taxonomic ranks (families and orders), and a wide variety of classifications and hypothetical phylogenies exists for this group of ca. 10,000 species. This confusion results in part from a lack of morphological features that are both variable in their expression or form species to species but coherent enough to be homologous, that is, similar and comparable across numerous different species and genera. DNA sequence data are ideal characters for both reasons: variable among taxa but comparable across all of them, at least for functionally important genes. Dr. Paul Wolf of Utah State University is sequencing DNA from the chloroplast photosynthetic gene for numerous fern species allied in the "dennstaedtioid" group, in order to reconstruct their phylogeny under the working assumption that mutational differences track the divergence of species through time. %%% An independent molecular set of data will provide a valuable tool for assessing the origins of various fern groups as well as for examining patterns of morphological and chromosomal variation. The dennstaedtioid ferns constitute a major component of the leptosporangiate or "higher" ferns, and the data from this study will ultimately be combined with results from other laboratories working on DNA sequencing in ferns to provide a phylogenetic framework for all major fern lineages.