There are no caterpillars in a wicked forest

Area of Science:

• Evolutionary biology
• Computational phylogenetics
• Population genetics

Background:

• Species trees depict historical population divergences, whereas gene trees illustrate gene copy ancestry.
• Rapid speciation can lead to gene trees incongruent with species trees, a phenomenon known as gene tree-species tree discordance.
• Understanding the conditions that generate anomalous gene trees is crucial for accurate phylogenetic inference.

Purpose of the Study:

• To establish a general constraint on gene tree topologies that cannot be anomalous.
• To investigate the properties of gene trees under the multispecies coalescent model, particularly in scenarios of rapid speciation.

Main Methods:

• Development of a novel combinatorial object termed 'population history'.
• Utilizing population histories to analyze coalescent events within ancestral populations.
• Mathematical proof establishing a constraint on gene tree topologies.

Main Results:

• Demonstration that gene trees with caterpillar topologies are never anomalous.
• The introduced population history object provides a framework for analyzing gene tree properties.
• The findings apply to species trees and gene trees of any size.

Conclusions:

• Gene trees with caterpillar topologies offer a reliable signal for species tree reconstruction, even in the presence of rapid speciation.
• The study provides a theoretical foundation for understanding gene tree-species tree discordance.
• This work contributes to the development of more robust methods for inferring species trees from molecular data.