Doebley John, Durbin Mary, Golenberg Edward M, Clegg Michael T, Ma Din Pow
Department of Plant Biology, University of Minnesota, St. Paul, MN, 55108, USA.
Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA.
Evolution. 1990 Jul;44(4):1097-1108. doi: 10.1111/j.1558-5646.1990.tb03828.x.
The full nucleotide sequences of the chloroplast encoded large subunit of ribulose-1,5-bisphosphate carboxylase (rbcL) are available for nine grass species and partial sequence data for one species. Relative rate tests of the "molecular clock" hypothesis suggest that rbcL evolved more rapidly in the lineage leading to Zea than in those leading to the other species. The estimated overall substitution rate for rbcL among these grasses is about 5 times 10 substitutions per site per year, or about one-half the synonymous rate. The nine full sequences were analyzed by the UPGMA, Wagner parsimony, maximum likelihood, and Fitch-Margoliash methods. The latter three methods produced trees with the same topology. This topology largely agrees with current taxonomic evidence regarding the relationships among these grasses. UPGMA produced a topology that conflicts more substantially with available taxonomic evidence. Statistical comparison of the three alternative topologies for the subfamilies Panicoideae, Pooideae and Bambusoideae failed to support one of these topologies over the others, reflecting the taxonomic ambiguities surrounding the relationships among these taxa. Phylogenetic analyses based on the partial sequences of all 10 species gave conflicting results with regard to the relationship between Hordeum and Triticum, both members of the tribe Triticeae. This indicates that rbcL sequences contain too little information to resolve relationships among genera within this tribe. Overall, the results suggest that rbcL sequence data can provide some new information concerning grass phylogeny, but that the amount of available data from this gene is too small to differentiate statistically among alternative topologies for the grasses. Conflicting results from parsimony, maximum likelihood, and Fitch-Margoliash methods proved useful in exploring the validity of assumptions underlying these methods.
已获得9种草种的叶绿体编码核酮糖-1,5-二磷酸羧化酶（rbcL）大亚基的完整核苷酸序列，以及1种草种的部分序列数据。“分子钟”假说的相对速率测试表明，rbcL在导致玉米的谱系中比在导致其他物种的谱系中进化得更快。这些草种中rbcL的估计总体替换率约为每年每个位点5×10个替换，约为同义替换率的一半。采用UPGMA、Wagner简约法、最大似然法和Fitch-Margoliash法对这9个完整序列进行了分析。后三种方法得到的树具有相同的拓扑结构。这种拓扑结构在很大程度上与当前关于这些草种间关系的分类学证据一致。UPGMA得到的拓扑结构与现有分类学证据的冲突更大。对黍亚科、早熟禾亚科和竹亚科的三种替代拓扑结构进行统计比较，未能支持其中一种拓扑结构优于其他拓扑结构，这反映了围绕这些分类群之间关系的分类学模糊性。基于所有10个物种的部分序列进行的系统发育分析，在小麦族的两个成员大麦和小麦之间的关系上给出了相互矛盾的结果。这表明rbcL序列包含的信息太少，无法解析该族内属间的关系。总体而言，结果表明rbcL序列数据可以提供一些关于草系统发育的新信息，但该基因的可用数据量太小，无法在草的替代拓扑结构之间进行统计学区分。简约法、最大似然法和Fitch-Margoliash法得出的相互矛盾的结果，在探索这些方法所依据假设的有效性方面被证明是有用的。
