Study shows successful fathers have less successful daughters

28 June 2007

The strongest and fittest of a species might be expected to produce the best offspring, but this is not always the case, scientists at the University of Edinburgh have found.

Studies of red deer published in this week's Nature journal suggest that the most successful males are more likely to produce less fertile daughters.

Male and female deer need different attributes to succeed. Genes which prove to be an advantage in fathers don't necessarily prove beneficial in daughters. Males who win fights for females go on to produce daughters who have fewer offspring, whereas the daughters of less successful males demonstrate higher fertility.

The research helps explain why, despite natural selection, there can still be broad biological diversity between individuals in a population.

Dr Loeske Kruuk and Dr Kathi Foerster, of the University of Edinburgh's School of Biological Sciences, and their colleagues have conducted a long-term study of a wild population of red deer on Rum, in the Inner Hebrides.

The Rum red deer population featured in BBC Television's Autumnwatch last year, which showed the violent drama played out each year during the rut.

Dr Kruuk explains, "In the mating season, stags compete to gain control of harems of females. A male will fight off other suitors and hope to mate with all his females. Only the biggest and strongest males, with the largest antlers, will win the battle to control large harems.

"Many males will go through their life, typically 10 years or so, without fathering any offspring."

The strongest males were defined as those which sired the most offspring.

The need to win a harem demonstrates high levels of selection pressure, which raises the question of why some individuals are much better adapted than others.

Dr Kruuk says, "Natural selection means that the most successful individuals pass on their genes more frequently than the losers, so in the next generation 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 between individuals in a population. This effect of the best males not producing the best daughters is possibly an important reason why such differences remain. Maybe the idea that some genes are better than others is just too simplistic: it depends on the sex of the individual animal."

Dr Kruuk adds "It is possible that the differences are attributable to the genes in question affecting levels of the hormone testosterone.

"High levels of testosterone could enhance male aggression, but we know from other species that they can also have adverse effects on female fertility. We're hoping further research on the red deer will be able to nail this suggestion."

The research was partly funded by the Natural Environment Research Council (NERC).

Further information

Loeske Kruuk
School of Biological Sciences
Mob: 07795 820974

Josephine Pemberton
School of Biological Sciences
Tel: 0131 650 5505

Catriona Kelly
Press and PR Office
Tel: 0131 651 4401

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Press release: 22/07

Study shows successful fathers have less successful daughters

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