An international team led by biologists from the University of Texas reported in a new study that species that reproduce asexually have more harmful genetic mutations than those species that utilize sexual reproduction.
Jose Maldonado, a doctoral student in biology at UTA and the lead author of the study, said that a form of asexual reproduction called parthenogenesis negatively affects animal genome evolution, which may lead to decreased biological diversity. This type of reproduction produces offspring from an unfertilized egg.
Parthenogenesis A.K.A. "Virgin Births" Explained
Most animals need to breed to reproduce, which means it needs an egg cell from the female and a sperm cell from the male. But a small subset of species produces offspring through asexual reproduction.
National Geographic explains that this type of asexual reproduction is called parthenogenesis, which allows species to have so-called "virgin births." Such events usually cause shock to caretakers as most creatures reproduce via sexual reproduction. For example, the zebra shark named Leonie from Australia suddenly had a virgin birth when three of her eggs hatched into living pups.
Moreover, there are two types of parthenogenesis. The first type is the automixis, in which an animal can merge a polar body with an egg to produce offspring. Automixis has been reported in some sharks, wherein a mother's genes are mixed to create offspring similar to the mother.
The second type of parthenogenesis is the apomixis, wherein the reproductive cells replicate via mitosis that duplicates to create two diploid cells that undergo meiosis to produce offspring that are clones of the mother. That means the offspring has the exact copy of the genes of its parent.
Parthenogenesis Leads to More Harmful Genetic Mutations
Although parthenogenesis is a natural form of asexual reproduction, it is generally believed to lead to more harmful genetic mutations than sexual reproduction.
Maldonado and his team tested this theory by studying the whiptail lizard called Aspidoscelis, which makes an excellent model to study the cellular mechanism of parthenogenesis and genomic sequences of a product of asexual reproduction. Phys.org compared whole mitochondrial genome data from asexual and sexual whiptail lizards to see how fast genetic mutations accumulate.
He explained that their study showed that the model accumulated more harmful mutations when it asexually reproduced compared to its sexually produced counterparts. The findings show why asexual reproduction is rare in nature and why sex is the most dominant form of reproduction in nature.
They repeated their experiment in multiple populations of the whiptail species in the US and came up with the same results. Their findings support theoretical predictions that the loss of sex will lead to an irreversible build-up of deleterious mutations because of lesser efficient purifying selection. The team concluded that sexual reproduction facilitates the removal of harmful genetic mutations.
The team discussed the full findings of their study titled "Parthenogenesis doubles the rate of amino acid substitution in whiptail mitochondria," published in the International Journal of Organic Evolution.
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