Thursday, June 28, 2007

Red deer study: Macho fathers can be confident that their sons will take after them, but their daughters are likely to be weaklings

Lewis Smith:

Research into the benefits of genes passed on by fathers has shown that what is good for sons may be detrimental to the development of daughters.

Red deer were chosen for the study but a similar genetic disadvantage is likely to be passed on by human fathers to daughters.

The findings show for the first time in animals that some genes are designed to benefit just one gender and can handicap the other sex.

It was found that the female offspring of the biggest and strongest stags were less successful at breeding and had fewer fawns during their lives than daughters of weedy males.

Professor Josephine Pemberton, of the University of Edinburgh, said it appeared that evolution was having a hard time finding a balance between serving the interests of both male and female offspring.

“Evolution can’t find an optimum for both sexes,” she said. “Males need to be big and burly with antlers and be really quite aggressive. Females don’t have to be so big, they don’t need to be aggressive and the ideal characteristics are different.”

To reach their conclusions, published in the journal Nature, researchers analysed the red deer population on the island of Rum, off the West Coast of Scotland.

Deer were introduced to the island in the mid-19th century and there is now a population of about 1,000, of which 300 are closely observed by scientists. Research data has been recorded on the deer since 1972 and last year the animals were some of the stars of the BBC Autumnwatch programme.

The red deer, Cervus elaphus, was considered ideal for the gene study because of the large difference in size and behav-iour between the sexes.

Success among stags was judged on the basis of how many fawns they sired. The biggest and strongest males, with the largest antlers, fight other stags during the rutting season to control large harems.

The findings are thought to explain why there is such a wide genetic diversity in animal populations despite the process of natural selection, by which all but the most successful genes should be weeded out.

Loeske Kruuk, of the University of Edinburgh, said: “Natural selection means the most successful individuals pass on their genes more frequently than the losers, so more individuals should be carrying those good genes.

“As time goes on we should expect the low-quality genes to be lost, causing less variation between individuals. But we still see huge differences.

“This effect of the best males not producing the best daughters is possibly an important reason why differences remain. Maybe the idea that some genes are better than others is too simplistic: it depends on the sex of the individual.”

In the mating season, Dr Kruuk said, stags competed to gain control of harems of females: “Only the biggest and strongest males, with the largest antlers, will win the battle.”

Katharina Foerster, of the Institute of Evolutionary Biology at the University of Edinburgh, led the study and said the results showed that “good genes” for males were not necessarily good for females.

Gender-specific fitness?

Sexual dimorphism with no costs takes some time

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