Manipulative mothers subdue show-off sons

Sep 12, 2011

The gaudy plumage and acrobatic displays of birds of paradise are a striking example of sexual selection, Charles Darwin's second great theory of evolution. But new research shows that this powerful process may collapse when mothers can decide whether to have a son or a daughter.

Choosing the sex of our offspring may seem totally beyond our control, but some animals have a remarkable capacity to manipulate this. The female eclectus parrot, for example, has been known to produce 20 sons in a row before switching to producing only daughters. Now, a team of has found that tight control over offspring sex ratios can have disastrous consequences for .

Led by Dr Tim Fawcett, a research fellow at the University of Bristol, the team used mathematical models and to investigate how control and sexual selection interact. With sex ratios fixed at 50, the scientists found the classical pattern of sexual selection, with males evolving elaborate courtship displays to attract females. But when they changed the models so that mothers could control the sex ratio of their offspring, they found a completely different pattern.

The research is published in the .

"The effect was dramatic," said Dr Fawcett. "When mothers choose the sex of their offspring, sexual selection collapses and male courtship displays disappear. This is because females no longer find the displays attractive."

The finding adds an unexpected twist to Darwin's theory of sexual selection. "Previously, we thought that females needed to find a showy male to produce the best offspring. But when they can control the sex ratio, this no longer matters. Mothers with drab partners do just as well," Dr Fawcett added.

The scientists now plan to put their theory to the test. If they are right, this may help us to understand the great diversity in male courtship displays seen across the animal kingdom.

"In many animals, including humans, sex is determined by the genes," Dr Fawcett explained, "while other animals have a much more flexible system. Some turtles, for example, produce sons when their eggs are kept cool and daughters when their eggs are kept hot. We expect to find strong differences in sexual selection between these systems."

Explore further: Rock-paper-scissors model helps researchers demonstrate benefits of high mutation rates

More information: "Sex-ratio control erodes sexual selection, revealing evolutionary feedback from adaptive plasticity", Tim W. Fawcett, Bram Kuijper, Franz J. Weissing and Ido Pen, Proceedings of the National Academy of Sciences (2011).

Related Stories

Small But Mighty Female Lizards Control Genetic Destiny

Apr 05, 2010

( -- "Be faithful in small things because it is in them that your strength lies." Mother Teresa's words echo throughout the world. They ring particularly true in the biological kingdom among brown ...

Why do we choose our mates? Ask Charles Darwin, prof says

Jun 16, 2009

Charles Darwin wrote about it 150 years ago: animals don't pick their mates by pure chance - it's a process that is deliberate and involves numerous factors. After decades of examining his work, experts agree that he pretty ...

Sex in the morning or the evening?

Jun 26, 2007

Most research on sexual conflict ignores the fact that the fitness pay-offs of mating may change drastically over a short timescale, for example over a single day.

Recommended for you

Does germ plasm accelerate evolution?

Apr 14, 2014

Scientists at The University of Nottingham have published research in the leading academic journal Science that challenges a long held belief about the way certain species of vertebrates evolved.

User comments : 0

More news stories

Gene removal could have implications beyond plant science

( —For thousands of years humans have been tinkering with plant genetics, even when they didn't realize that is what they were doing, in an effort to make stronger, healthier crops that endured climates better, ...

Making 'bucky-balls' in spin-out's sights

( —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...