Toronto, Jan 13 (IANS): Researchers from the University of Toronto have found that species which reproduce sexually rather than asexually are healthier over time because they do not accumulate harmful mutations.

"The findings allow us to understand why an enormous diversity of species around the world go through the laborious process of sexual reproduction," said lead researcher Jesse Hollister who completed the research while working at University of Toronto Mississauga's department of biology.

Asexual reproduction leads to a build up of deleterious mutations over time - it is called Muller's Ratchet.

"The species' average fitness is reduced and they are less able to compete in the ecological arena than sexual species, so they have an increased probability of extinction," Hollister explained.

The evening primrose was the ideal system for studying the evolutionary importance of sex for the team because about 30 percent of the species in the genus have evolved to reproduce asexually, each at a different time.

With the assistance of the 1,000 plant transcriptome project, the University of Toronto researchers were able to examine 30 pairs of species.

One species in the pair reproduced sexually while the other asexually.

Some of the asexually reproducing species were younger than others in evolutionary terms, allowing the researchers to see the effects of asexual reproduction over time.

"What we found was exactly what we predicted based on theory," Hollister said.

"The study allowed us to unlock part of the mystery of why sex is so common: it is good for your health, at least if you are a plant," he concluded.

The research was published in the journal Molecular Biology and Evolution.