Asexual reproduction leads to harmful genetic mutations

A team led by biologists from the University of Texas at Arlington has published a study that supports the theory that species that reproduce asexually have more damaging genetic mutations than those that use sexual reproduction.

José Maldonado, a UTA biology doctoral student, is the lead author of the new paper, titled “Parthenogenesis Doubles the Rate of Amino Acid Substitution in Whiptail Mitochondria.” It was published in May in Evolutionthe flagship journal of evolutionary biology.

Coauthors include TJ Firneno, a postdoctoral research associate at the University of Denver who received his Ph.D. from UTA in 2020; Alexander Hall, a Thermo Fisher Scientific product applications specialist who received a Ph.D. from UTA in 2016; and Matt Fujita, an associate professor of biology at UTA, who is Maldonado’s faculty adviser and previously held the same position for Firneno and Hall.

Parthenogenesis is a natural form of asexual reproduction in which the growth and development of embryos occur without fertilization by sperm. In general, sexual reproduction is thought to lead to less damage genetic mutations than asexual reproduction.

In their new study, Maldonado and his co-authors tested this theory by studying Aspidoscelis, a genus of whiptail lizards. Due to their high abundance and distribution in the southwestern United States and northern Mexico, these reptiles are an excellent model system to study the fundamental cellular mechanisms of parthenogenesis and the genomic consequences of asexuality.

The team used complete mitochondrial genome data from asexual and sexual whiptail lizards to investigate their prediction that parthenogenetic lineages accumulate mutations faster than sexual lineages.

“Our study demonstrates that when whiptail lizards switch from reproducing sexually to asexually, the accumulation of harmful mutations in the mitochondrial genome occurs,” Maldonado said. “If asexuals accumulate more harmful mutations than their sexual counterparts, as our findings show, this could explain why asexual reproduction is rare in nature and why sex is the dominant form of reproduction in the natural world”.

The team sampled multiple populations of both asexual and sexual whiptail species throughout the southwestern United States and received additional tissue samples from the collections of the Burke Museum of Natural History and Culture in Seattle and the American Museum of American History. Native in New York City.

Their research showed that the transition to asexuality led to relaxed natural selection in parthenogenetic lizards and the accumulation of non-synonymous mutations, which change the protein sequences of a gene and are often subject to natural selection. This supports previous theoretical predictions that “loss of sex should lead to an irreversible accumulation of deleterious mutations due to a reduction in the efficiency of purifying selection, and sex facilitates the removal of deleterious mutations,” they wrote.

“The main finding of our study is that asexual vertebrates, or at least these lizards, accumulate amino acid substitutionsthat could be potentially bad for the organism, at a much higher rate than sexual species,” Firneno said. “This is important because there is the paradox that it is much more expensive to reproduce sexually, but that is the widespread way of reproduction. ”