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

Studies of red deer 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 School of Biological Sciences, and their colleagues conducted a long-term study of a wild population of red deer on Rum, in the Inner Hebrides.

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.”

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