Sexual selection and the evolution of evolvability

Abstract

Here we show that sexual selection can have an effect on the rate of mutation. We simulated the fate of a genetic modifier of the mutation rate in a sexual population with and without sexual selection (modelled using a female choice mechanism). Female choice for 'good genes' should reduce variability among male subjects, leaving insufficient differences to maintain female preferences. However, female choice can actually increase genetic variability by supporting a higher mutation rate in sexually selected traits. Increasing the mutation rate will be selected against because of the resulting decline in mean fitness. However, it also increases the probability of rare beneficial mutations arising, and mating skew caused by female preferences for male subjects carrying those beneficials with few deleterious mutations ('good genes') can lead to a mutation rate above that expected under natural selection. A choice of two male subjects was sufficient for there to be a twofold increase in the mutation rate as opposed to a decrease found under random mating.

Mutability and evolvability: Indirect selection for mutability

“…Petrie and Roberts (2007) have recently described a theoretical example of increased mutation rate based on female choice. Mutator alleles can also be favored by strong selection for phenotypic variation, such as that imposed by immunological attack against pathogens, together with stable linkage to beneficial mutations, provided by haploidy in microorganisms.…”

Evolutionary genetics: Sexually selected mutation rates

“…However, Petrie and Roberts (2006) show that sexual selection makes a difference. They consider evolution of the mutation rate in a sexual population in which females pick the best (i.e.…”

“…In this case, males with beneficial mutations gain most of the matings, whereas other males lose out irrespective of the number of deleterious alleles they carry. This leads to a net selective advantage for linked mutator genes (Petrie and Roberts (2006) only consider tightly linked modifiers of the mutation rate). Petrie and Roberts (2006) suggest that female preference, mutator alleles and condition-dependent male ornaments interact in such a way that sexual selection generates self-sustaining variability.…”

“…This leads to a net selective advantage for linked mutator genes (Petrie and Roberts (2006) only consider tightly linked modifiers of the mutation rate). Petrie and Roberts (2006) suggest that female preference, mutator alleles and condition-dependent male ornaments interact in such a way that sexual selection generates self-sustaining variability. Mate preference indirectly causes mutators to be favoured and these increase variance in genetic quality and hence increase the selective benefit on preference itself.…”

“…But persistent selection on ornaments and condition should cause genetic variation in male fitness to be depleted rapidly, thereby eliminating any advantage to female mate preference -a problem known as the 'lek paradox'. Recently, Petrie and Roberts (2006) proposed that female mate choice indirectly selects for elevated rates of mutation, and claim this increases the amount of available genetic variation faster than sexual selection can erode it. Their solution provides an intriguing resolution to the lek paradox, but can it really account for the maintenance of genetic variation in fitness associated with sexual ornaments?…”