Created on 15th June 2016
Eukaryotes carry numerous asexual cytoplasmic genomes (mitochondria and chloroplasts). Lacking recombination, asexual genomes suffer from impaired adaptive evolution. Yet, empirical evidence suggests that cytoplasmic genomes do not suffer this limitation of asexual reproduction. Here we use computational models to show that the unique biology of cytoplasmic genomes---specifically their organization into host cells and their uniparental inheritance---enable them to undergo adaptive evolution more effectively than comparable free-living asexual genomes. Uniparental inheritance decreases competition between different beneficial substitutions (clonal interference), reduces genetic hitchhiking of deleterious substitutions during selective sweeps, and promotes adaptive evolution by increasing the level of beneficial substitutions relative to deleterious substitutions. When cytoplasmic genome inheritance is biparental, a tight transmission bottleneck aids adaptive evolution. Nevertheless, adaptive evolution is always more efficient when inheritance is uniparental. Our findings help explain empirical observations that cytoplasmic genomes---despite their asexual mode of reproduction---can readily undergo adaptive evolution.Show more
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