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Most animals on Earth have two sexes, male and female, which mix their genes when they reproduce. However, there are exceptions to the rule. Some species are exclusively female, do not practice sex and reproduce by cloning.
This is the case of a showy Australian grasshopper named, very appropriately, Warramaba virgo. The young are born by partenogenesis, which implies that the egg develops into an embryo without being fertilized by a sperm. No males or sex are needed. Is it possible to live like this and be successful from an evolutionary point of view?
Well, it seems that yes. An international team has studied W. virgo and has found that the species arose about 250,000 years ago from a cross between two other different species of sexually reproducing grasshoppers.
As they conclude in the journal ‘Science’, giving up sex for so long did not affect their ability to survive and reproduce. On the contrary, he was just as successful as his counterparts who do have sex. For researchers, this is fascinating information about evolution.
The usual method of reproduction, which involves interbreeding between males and females, “increases the genetic diversity and ecological success of a species,” says Michael Kearney of the University of Melbourne. Additionally, it helps purge a population of bad mutation combinations. In contrast, in parthenogenetic species all members have virtually identical genes. This means that they may be less able to adapt when the environment changes and may accumulate bad mutations that worsen their fitness. But the new findings challenge current evolutionary theory about the advantages of sexual reproduction.
no mutations
The conclusion of the investigation is that the insect became parthenogenetic but without costs. In theory, these animals “should be suffering from parasites and a high load of bad mutations. However, our study does not find any disadvantage for W. virgo compared to other species of grasshoppers that reproduce sexually. In fact, W. virgo it has even managed to spread successfully from the west to the east of Australia, unlike its sexual relatives, ”says the researcher.
In addition, this natural celibacy has the advantage of not ‘wasting time’ looking for the better half. “Finding a mate takes time and energy and carries a higher risk of predation – animals that mate often are in greater danger of being attacked by predators. If we can kill off the males and still have viable offspring and the species thrives, then why bother with sex?” asks study co-author Ary Hoffmann.
a single clone
The study analyzed more than 1,500 genetic markers to assess genetic diversity in W. virgo and found almost no variation, in stark contrast to related species of sexually reproducing grasshoppers. “The species seems to have developed from a single highly successful clone,” says Hoffmann.
Based on the number and nature of the mutations, the researchers estimated that W. virgo evolved from a hybrid mating between two other species of grasshoppers (W. whitei y W. flavolineata) more than 250,000 years ago. They also showed that the parthenogen had no advantage over its parent species in a number of physiological traits such as tolerance to heat and cold, rate of metabolism, the number and size of its eggs, how long they take to mature, and how long they live.
“With so many benefits of giving up sex, it’s surprising that parthenogenetic species aren’t more common. Our research proposes that this rarity is likely due to constraints on origin rather than rapid extinction,” Kearney said. That is to say, more species do not renounce sex because developing parthenogenesis must be very difficult.
While parthenogenetic species are extremely rare, some are found in Australia. W. virgo It feeds on shrubs and it seems that it will continue to occupy gardens for many more years.
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