Characterizing positive and negative selection and their phylogenetic effects.

Area of Science:

• Evolutionary biology
• Bioinformatics
• Genomics

Background:

• Phylogenetic analysis typically assumes neutral evolution and site independence.
• Gene families may exhibit varying selective pressures across codon positions.
• Existing phylogenetic methods may not adequately account for non-neutral evolutionary processes.

Purpose of the Study:

• To evaluate the robustness of standard phylogenetic methods when applied to gene families with varying selective pressures.
• To investigate the potential for functional or structural signals to compete with ancestral signals in phylogenetic reconstruction.
• To explore how selection, particularly positive selection, impacts phylogenetic signal.

Main Methods:

• Categorizing codon positions within gene families based on average pairwise dN/dS ratios.
• Applying standard phylogenetic reconstruction methods (parsimony, distance, likelihood) to different codon position bins.
• Simulating sequence evolution on 3D lattices with folding constraints and functional changes to model positive selection.

Main Results:

• Phylogenetic signal was less robust for codon positions under strong negative or positive selection compared to neutral sites.
• Standard phylogenetic methods showed reduced accuracy when applied to sites with strong selective pressures.
• Simulations demonstrated that functional convergence can lead to phylogenetic trees reflecting functional signal rather than true ancestral relationships.

Conclusions:

• Standard phylogenetic methods are less reliable for inferring deep evolutionary history in genes experiencing strong selection.
• Functional and ancestral signals can be distinct and potentially conflicting in phylogenetic analyses.
• The presence of functional constraints and selection can promote sequence convergence, complicating ancestral state reconstruction.