Adaptive Evolution Is Substantially Impeded by Hill-Robertson Interference in Drosophila

Area of Science:

• Evolutionary genetics
• Population genetics
• Genomics

Background:

• Hill-Robertson interference (HRi) is a theoretical impediment to natural selection's efficiency.
• Previous research has not quantified HRi's genome-wide impact on adaptive evolution rates.

Purpose of the Study:

• To estimate the quantitative impact of HRi on adaptive evolution in the coding genome of Drosophila melanogaster.
• To investigate how genomic factors influence HRi's effect on adaptive substitution rates.

Main Methods:

• Compiled a dataset of 6,141 autosomal protein-coding genes from Drosophila.
• Estimated polymorphism and divergence levels to calculate the rate of adaptive evolution using a modified McDonald-Kreitman test.
• Analyzed correlations between adaptive substitution rates and recombination, mutation rates, and gene density.

Main Results:

• The rate of adaptive amino acid substitution positively correlates with recombination and mutation rates, and negatively with gene density.
• HRi diminishes the overall rate of adaptive evolution by approximately 27%.
• Genes in gene-poor regions with low mutation rates lose ~17% of adaptive substitutions, while those in gene-rich regions with high mutation rates lose ~60%.

Conclusions:

• HRi significantly hampers adaptive evolution in Drosophila.
• Genomic variations in recombination, mutation rates, and gene density modulate the strength of HRi's impact on adaptive evolution.