Continuity in evolution: on the nature of transitions

Area of Science:

• Evolutionary biology
• Molecular biology
• Genetics

Background:

• Distinguishing continuous from discontinuous evolutionary change requires a quantitative measure of nearness between phenotypes.
• Phenotypic nearness is defined by the probability of transitioning between phenotypes via genotypic changes.

Purpose of the Study:

• To develop and apply a nearness relation for phenotypes to study evolutionary change.
• To characterize discontinuous shape transformations in transfer RNA (tRNA) secondary structures.
• To investigate the relationship between sudden adaptive progress and discontinuous shape transformations in RNA evolution.

Main Methods:

• Calculating the shape neighborhood of transfer RNA (tRNA) secondary structures to define a nearness relation.
• Simulating populations of replicating and mutating RNA under selection.
• Analyzing the correlation between discontinuous shape transformations and adaptive progress.

Main Results:

• A nearness relation based on genotype accessibility was established.
• Discontinuous shape transformations in RNA were characterized using shape neighborhoods.
• Simulations showed that sudden adaptive progress often coincides with discontinuous shape transformations, highlighting the role of neutral genetic drift.

Conclusions:

• The developed nearness relation provides a framework for distinguishing continuous and discontinuous evolutionary change.
• Discontinuous shape transformations in RNA are significant evolutionary events.
• Neutral genetic drift plays a crucial role in enabling these discontinuous transformations and subsequent adaptive progress.