Not All "Fit" Survive

Scientists at the Australian National University studied the breeding behavior of European bank voles, a small rodent found in Europe and Great Britain, and discovered that reproductive success does not run in the family.

The researchers observed that the males which have the genes for behavioral dominance were most likely to win mates but the female siblings also carrying the gene were less successful, producing smaller litter sizes. On the other hand, females which do not carry the genes had bigger litter sizes. This implies that even if genes that were maladaptive for one sex were to some extent carried through to the next generation by its more successful opposite-sex siblings, the difference in the genes' effects for the two sexes was so strong that this would be unlikely to maintain genetic variance by itself.

They also found that the dominant gene was only helpful for males when it was rare in the population. This process is called negative frequency dependence, which is important in maintaining genetic diversity. "Males with the dominant gene are quite aggressive, so when the gene gets more common in a population, dominant males are more likely to spend their time fighting, and the tame males get an advantage at that point," said Jussi Lehtonen, one of the authors of the study.

Read the complete story at http://news.anu.edu.au/?p=12331.