Comparing Nuclear and Chloroplast Phylogenies in Saxifragaceae and Related Rosids

小行星9307000 叶绿体基因组（cpDNA）变异的系统发育分析在过去十年的植物系统研究中占据主导地位。 虽然在检索叶绿体基因组学中存在许多cpDNA变异的优点，但几个因素可能潜在地导致实际生物和基于cpDNA的叶绿体基因组学之间的不一致，包括分类群密度、进化速率的异质性、谱系分选和叶绿体捕获。 因此，系统分类学家一致认为，比较细胞核和叶绿体DNA为基础的遗传学是至关重要的. 因此，该项目将解决植物系统学的一个重要需求：现有的基于cpDNA的同源基因与来自核基因序列的同源基因的比较。 所采取的方法将是分层的，从物种水平开始，移动到密切相关的属群，所有30个属的虎耳草科狭义，并最终到相关的rosid科。 根据研究的分类学水平，将从整个内部转录间隔区（ITS）或核核糖体DNA（rDNA）的18S区域获得序列。 初步数据表明，这些区域正在以适当的速度为每一个这些分类水平的演变。 基于cpDNA和核DNA的同源性的比较在组中特别重要，例如虎耳草科s.s.，它们以杂交和叶绿体捕获而闻名，因此可能怀疑它们是以cpDNA为基础的杂交。 提出的分层方法也可能提供新的见解的模式和过去的杂交系统发育的影响。

9307000 Soltis Phylogenetic analysis of variation in the chloroplast genome (cpDNA) has dominated the past decade of systematic research in plants. Although there are numerous advantages of cpDNA variation in retrieving phylogeny, several factors can potentially, contribute to discordance between the actual organismal and cpDNA- based phylogenies, including taxon density, heterogeneity of evolutionary rates, lineage sorting, and chloroplast capture. Systematists therefore concur that comparison of nuclear and cpDNA- based phylogenies is critical. This project will therefore address an important need in plant systematics: the comparison of existing cpDNA-based phylogenies with those derived from nuclear gene sequences. The approach taken will be hierarchical beginning at the species level, moving to closely related groups of genera, all 30 genera of Saxifragaceae sensu stricto, and ultimately to associated rosid families. Sequences will be obtained from the entire internal transcribed spacer (ITS) or 18S regions of nuclear ribosomal DNA (rDNA), depending on the taxonomic level of inquiry. Preliminary data indicate that these regions are evolving at appropriate rates for each of these taxonomic levels. Comparison of cpDNA-and nuclear DNA-based phylogenies is particularly important in groups, such as Saxifragaceae s.s., that are noted for hybridization and chloroplast capture and for which the cpDNA-based phylogenies may consequently be suspect. The hierarchical approach proposed may also provide new insights into the patterns and phylogenetic impact of past hybridization.