February 4, 2023

Goldteju Tupinambis teguixine. Credit: Wikipedia/CC BY-SA 3.0

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 harmful genetic mutations than those that use sexual reproduction.

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

Co-authors include TJ Firneno, a postdoctoral research associate at the University of Denver who completed his Ph.D. from UTA in 2020; Alexander Hall, a product application specialist at Thermo Fisher Scientific who holds a Ph.D. from UTA in 2016; and Matt Fujita, an associate professor of biology at UTA, Maldonado’s faculty advisor and previously in the same role for Firneno and Hall.

Parthenogenesis is a natural form of asexual reproduction in which the growth and development of embryos occurs without fertilization by sperm. It is generally accepted that sexual reproduction leads to less harmful 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 full mitochondrial genome data from asexual and sexual whiptail lizards to investigate their prediction that parthenogenetic lines accumulate mutations faster than sexual lines.

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“Our study shows that when whiptail lizards transition from sexual reproduction to asexual, it is followed by the accumulation of deleterious mutations in the mitochondrial genome,” Maldonado said. “If asexuals accumulate more deleterious 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 in the southwestern United States and received additional tissue samples from collections at the Burke Museum of Natural History and Culture in Seattle and the American Museum of Natural History in New York City.

Their research showed that the transition to asexuality led to relaxed natural selection in parthenogenetic lizards and the build-up of non-synonymous mutations, which alter 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 build-up 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 substitutions, which can potentially be bad for the organism, at a much higher rate than sexual species,” Firneno said. “This is important because there is a paradox that it is much more expensive to reproduce sexually, but it is the pervasive form of reproduction.”

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More information:
Jose A. Maldonado et al, Parthenogenesis doubles the rate of amino acid substitution in whiptail mitochondria, Evolution (2022). DOI: 10.1111/evo.14509

Provided by the University of Texas at Arlington

Quote: Asexual reproduction leads to harmful genetic mutations (2022, August 1), retrieved August 1, 2022 from https://phys.org/news/2022-08-asexual-reproduction-genetic-mutations.html

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