An Extension of the Kimura Two-Parameter Model to the Natural Evolutionary Process

Area of Science:

• Evolutionary biology
• Molecular evolution
• Bioinformatics

Background:

• Accurate genetic distance estimation is fundamental for evolutionary biology research.
• Existing models like Kimura two-parameter (K2P) may not fully account for evolutionary complexities.
• Gaps (insertions/deletions) significantly impact genetic difference calculations.

Purpose of the Study:

• To extend the Kimura two-parameter (K2P) model by incorporating gaps.
• To introduce a novel measure for estimating genetic difference considering nucleotide changes and gaps.
• To assess the impact of different evolutionary models on species identification and phylogenetic analyses.

Main Methods:

• Extension of the Kimura two-parameter (K2P) model to include gap considerations.
• Development of a new genetic difference measure accounting for insertions and deletions.
• Application of models to the nuclear ribosomal DNA internal transcribed spacer 2 region of the genus Physalis.

Main Results:

• The new model, which does not remove gap sites, resulted in 16.9% overlap between intraspecific and interspecific genetic differences, compared to 43.2% and 22.7% for K2P variants.
• The new model identified 29 pairs with zero interspecific genetic difference, while the K2P model identified 50.
• The K2P model overestimated genetic differences, misclassifying 21 non-identical sequence pairs as identical.

Conclusions:

• Estimating genetic differences requires models that account for insertions and deletions alongside substitutions.
• The choice of evolutionary model significantly influences species identification and phylogenetic outcomes.
• The proposed model offers a more accurate assessment of genetic divergence, crucial for evolutionary studies.