Why Concatenation Fails Near the Anomaly Zone

Area of Science:

• Phylogenetics
• Computational Biology
• Evolutionary Biology

Background:

• Genome-scale sequencing aids species tree recovery but faces challenges with short, deep branches.
• Concatenating gene alignments is a strategy to improve phylogenetic inference.
• Incomplete lineage sorting can hinder accurate species tree reconstruction.

Purpose of the Study:

• Investigate the failure of likelihood-based methods in species tree reconstruction from concatenated data.
• Analyze method performance within and outside the anomaly zone.
• Understand the impact of incomplete lineage sorting on phylogenetic accuracy.

Main Methods:

• Utilized coalescent theory to analyze phylogenetic signal.
• Evaluated maximum-parsimony and maximum-likelihood methods on concatenated gene alignments.
• Focused on a rooted, asymmetric four-taxon species tree model.

Main Results:

• Coalescent theory predicts maximum-parsimony success in the anomaly zone.
• Maximum-likelihood methods fail to accurately recover species trees both inside and outside the anomaly zone.
• Failure of likelihood methods is linked to substitution costs on discordant gene tree branches.

Conclusions:

• Likelihood-based methods demonstrate limitations in reconstructing species trees from concatenated data under incomplete lineage sorting.
• Maximum-parsimony offers a more robust approach in challenging phylogenetic scenarios.
• Further research is needed to enhance the performance of phylogenetic inference methods.