Pol Diego, Escapa Ignacio H
CONICET, Museo Paleontológico Egidio Feruglio, Avenida Fontana 140, Trelew U9100GYO, Chubut, Argentina.
Cladistics. 2009 Oct;25(5):515-527. doi: 10.1111/j.1096-0031.2009.00258.x. Epub 2009 May 21.
A common problem in phylogenetic analysis is the presence of unstable taxa that are depicted in multiple positions in optimal topologies. These uncertainties are reflected in strict consensus trees with polytomies that hamper the interpretation of the phylogenetic results. We propose a protocol for detecting unstable branches (either terminal taxa or clades) and identifying particular characters related to their instability in cladistic analysis. This procedure is based on an iterative evaluation of the agreement of triplets among the optimal topologies (i.e. most-parsimonious trees, MPTs) and examination of character optimizations on these trees. Different types of characters underlying the unstable behaviour of taxa are detected: those with conflicting scorings that support alternative positions of problematic taxa and those with missing data in the unstable taxa that could reduce their instability if they are scored. The entire process is automated through a TNT script that provides a list of characters related to the instability of each unstable taxon. The outcome of this procedure can be used as a guide for further research efforts focused on the revision or addition of (morphological or molecular) phylogenetic data for elucidating the affinities of unstable taxa. © The Willi Hennig Society 2009.
系统发育分析中的一个常见问题是存在不稳定的分类单元，这些分类单元在最优拓扑结构中的多个位置被描绘出来。这些不确定性反映在具有多歧分支的严格合意树中，这妨碍了对系统发育结果的解释。我们提出了一种协议，用于在分支系统分析中检测不稳定分支（无论是末端分类单元还是分支），并识别与其不稳定性相关的特定特征。该程序基于对最优拓扑结构（即最简约树，MPT）中三元组一致性的迭代评估以及对这些树上特征优化的检查。检测到分类单元不稳定行为背后的不同类型特征：那些具有冲突评分以支持有问题分类单元的替代位置的特征，以及那些在不稳定分类单元中存在缺失数据的特征，如果对这些数据进行评分，可能会降低其不稳定性。整个过程通过一个TNT脚本实现自动化，该脚本提供了与每个不稳定分类单元的不稳定性相关的特征列表。该程序的结果可作为进一步研究工作的指南，这些研究工作专注于修订或添加（形态学或分子）系统发育数据，以阐明不稳定分类单元的亲缘关系。 © 威利·亨尼希协会2009年。
