Phylogeny imbalance: taxonomic level matters.

Area of Science:

• Evolutionary Biology
• Phylogenetics
• Systematic Biology

Background:

• Phylogenetic trees visually represent evolutionary relationships.
• Tree shape (topology) can provide insights into evolutionary processes.
• Understanding tree asymmetry is crucial for accurate evolutionary interpretations.

Purpose of the Study:

• To investigate differences in phylogenetic tree symmetry at various hierarchical levels.
• To determine if tree imbalance varies between species-level and higher-level phylogenies.
• To assess the impact of species richness on tree topology asymmetry.

Main Methods:

• Analysis of 61 phylogenies with superspecific taxa.
• Comparison of tree imbalance with and without considering species richness.
• Evaluation of node imbalance based on the number of higher taxa versus species descendants.
• Utilized an imbalance measure accommodating polytomies.

Main Results:

• Phylogenetic trees were significantly more asymmetric (unbalanced) at higher taxonomic levels compared to species-level analyses.
• Nodes with more higher taxa descendants showed greater imbalance than those with an equivalent number of species descendants.
• Species richness significantly influenced the perceived asymmetry of phylogenetic trees.

Conclusions:

• Phylogenetic tree asymmetry differs across hierarchical levels, necessitating distinct analytical approaches.
• Species-level and higher-level phylogenies should not be treated as equivalent due to topological differences.
• The findings caution against generalizations about tree shape without considering the taxonomic scope.