Graybeal A
Department of Zoology, University of Texas, Austin, Texas 78712,
Syst Biol. 1998 Mar;47(1):9-17. doi: 10.1080/106351598260996.
The effects on phylogenetic accuracy of adding characters and/or taxa were explored using data generated by computer simulation. The conditions of this study were constrained but allowed for systematic investigation of certain parameters. The starting point for the study was a four-taxon tree in the "Felsenstein zone," representing a difficult phylogenetic problem with an extreme situation of long branch attraction. Taxa were added sequentially to this tree in a manner specifically designed to break up the long branches, and for each tree data matrices of different sizes were simulated. Phylogenetic trees were reconstructed from these data using the criteria of parsimony and maximum likelihood. Phylogenetic accuracy was measured in three ways: (1) proportion of trees that are completely correct, (2) proportion of correctly reconstructed branches in all trees, and (3) proportion of trees in which the original four-taxon statement is correctly reconstructed. Accuracy improved dramatically with the addition of taxa and much more slowly with the addition of characters. If taxa can be added to break up long branches, it is much more preferable to add taxa than characters.
利用计算机模拟生成的数据，探讨了添加性状和/或分类单元对系统发育准确性的影响。本研究的条件受到限制，但允许对某些参数进行系统研究。该研究的起点是“费尔斯滕森区域”中的一个四分类单元树，它代表了一个具有长枝吸引极端情况的困难系统发育问题。分类单元以专门设计的方式依次添加到这棵树上，以打破长枝，并且针对每棵树模拟不同大小的数据矩阵。使用简约标准和最大似然法从这些数据中重建系统发育树。系统发育准确性通过三种方式衡量：（1）完全正确的树的比例，（2）所有树中正确重建分支的比例，以及（3）原始四分类单元陈述被正确重建的树的比例。随着分类单元的添加，准确性显著提高，而随着性状的添加，提高速度要慢得多。如果可以添加分类单元来打破长枝，那么添加分类单元比添加性状更可取。
