Scots scientists test the costs and benefits of sex
Stirling University use water fleas to prove sex helps next generation of species resist infection.
Scots scientists have taken a new approach to test the costs and benefits of sex.
A team of experts from Stirling University discovered sex can help the next generation of species resist infection.
The theory has been difficult to test as most animals or organisms are either wholly sexual or clonal so cannot be compared easily.
Some animal and plant species can reproduce without sex, such as komodo dragons, starfish and bananas, but sex is still the dominant mode of reproduction in the natural world.
But using an insect that can reproduce both with and without sex - the water flea - researchers found sexually produced offspring were more than twice as resistant to infectious disease as their clonal sisters.
Dr Stuart Auld, of the university's Faculty of Natural Sciences, said: "One of the oldest questions in evolutionary biology is, why does sex exist when it uses up so much time and energy?
"Sex explains the presence of the peacock's tail, the stag's antlers and the male bird of paradise's elaborate dance.
"But if a female of any of these species produced offspring on her own, without sex, her offspring should come to dominate, while the other females watch the redundant males fighting and dancing.
"So, why are we not surrounded by clonal organisms?"
He explained: "By comparing clonal and sexual daughters from the same mothers, we found sexually produced offspring get less sick than offspring that were produced clonally.
"The ever-present need to evade disease can explain why sex persists in the natural world in spite of the costs."
The water fleas and their parasites were collected from the wild. Sexual and clonally produced daughters were harvested from the wild waterfleas and these offspring were exposed to the parasites under controlled laboratory conditions.