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Evidence & discussions of hard polytomy

Evidence & discussions of hard polytomy


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Phylogenetic trees with >2 branches on a node are polytomic, and polytomy can appear on trees for two reasons. Firstly a lack of information in the data prevents proper resolution within a clade, called soft polytomy. Alternatively, hard polytomy may exist, this is when there truly is a simultaneous split from one lineage (species) in to more than two. Yang states that "it may be argued that hard polytomies do not exist" but makes no citation or attempts at theoretical discussion. Are there any papers which discuss the theoretical possibility of hard polytomy and any evidence of it occurring?

Image from http://biology.fullerton.edu/biol404/phylo/polytomies.html


I think that changes in features that determine a node may happen in parallel or close together in a sequence. If the fossil record is not complete enough then the cladogram has to contain these stars. From a stochastic statistic point of view, although unlikely, it could actually happen that 2 or more characteristics develop exactly during a similar time frame, so from a philosophical point of view, I disagree with yang.


You might want to have a look at some of these: Patterns of speciation and limits to phylogenetic resolution, Molecular polytomies, Problems with "soft" polytomies, and Polytomies, the power of phylogenetic inference, and the stochastic nature of molecular evolution.


Watch the video: How to Understand Evolutionary Trees (September 2022).


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