Patterns and determinants of mitogenomic evolution in Bilateria

Area of Science:

• Evolutionary Biology
• Genomics
• Animal Evolution

Background:

• Mitochondrial genome architecture is remarkably conserved in some animal lineages but variable in others.
• The evolutionary drivers behind this architectural disparity remain largely unknown.

Purpose of the Study:

• To investigate the influence of locomotory capacity and parasitic lifestyle on animal mitochondrial genome evolutionary rates.
• To explore factors contributing to variability in mitochondrial genome architecture across bilaterians.

Main Methods:

• Analysis of over 10,000 bilaterian mitochondrial genomes.
• Comparative analysis of gene order rearrangement and sequence evolution rates.
• Assessment of correlations between architectural evolution and ecological factors like locomotion and parasitism.

Main Results:

• Double-stranded architecture is likely ancestral for major animal radiations.
• Over twenty transitions to single-stranded architectures and state-reversals were identified.
• Gene order and sequence evolution rates correlate positively and are accelerated in single-stranded genomes, parasites, and species with low locomotory capacity.
• Mitogenome size negatively correlates with evolutionary rates; effective population size is decoupled.
• Endotherms show slower evolution than ectotherms in Bilateria, but faster in Chordata.

Conclusions:

• Ecological factors, particularly locomotory capacity and parasitic lifestyle, are major drivers of mitochondrial genome architectural evolution through purifying selection.
• While ecological pressures are significant, other variables are necessary for a complete understanding of observed patterns.