Parthenogenesis doubles the rate of amino acid substitution in Whiptail mitochondria

Sexual reproduction is ubiquitous in the natural world, suggesting that
sex must have extensive benefits to overcome the cost of males compared to
asexual reproduction. One hypothesized advantage of sex with strong
theoretical support is that sex plays a role in removing deleterious
mutations from the genome. Theory predicts that transitions to asexuality
should lead to the suppression of recombination and segregation and, in
turn, weakened natural selection, allowing for the accumulation of
slightly deleterious mutations. We tested this prediction by estimating
the dN/dS ratios in asexual vertebrate lineages in the
genus Aspidoscelis using whole mitochondrial genomes
from seven asexual and five sexual species. We found higher
dN/dS ratios in asexual Aspidoscelis species,
indicating that asexual whiptails accumulate non-synonymous substitutions
due to weaker purifying selection. Additionally, we estimated nucleotide
diversity and found that asexuals harbor significantly less diversity.
Thus, despite their recent origins, slightly deleterious mutations
accumulated rapidly enough in asexual lineages to be detected. We provided
empirical evidence to corroborate the connection between asexuality and
increased amino acid substitutions in asexual vertebrate
lineages.