Unstable taxa in cladistic analysis: identification and assesment of relevant characters

POL, D.; ESCAPA, I.

CLADISTICS (PRINT)

Blackwell Publishing Ltd.

Lugar: London; Año: 2009 vol. 25 p. 515 - 527

0748-3007

A common problem in phylogenetic analysis is the presence of unstable taxa that aredepicted in multiple positions in the optimal topologies. These uncertainties are reflected instrict consensus trees with polytomies that difficult the interpretation of the phylogeneticresults. We propose a protocol for detecting unstable branches (either terminal taxa or clades) and identifying the 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., MPTs) and the examination of character optimizations on these trees. Different types of characters underlying the unstable behavior of taxa are detected: those with conflictive 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 phylogenetic data for elucidating the affinities of unstable taxa.