Life history variation in male mate choice in Drosophila melanogaster

Variation in life history arises when individuals adopt alternative strategies for allocating finite resources to different traits to maximize fitness. Optimal strategies can vary not only between, but also within, species, and in particular between males and females. Variation in life histories can therefore affect the relative importance and impact of sexual selection, and this will itself feed back into how life histories evolve. Previous work has revealed that female mate choice tends to decline with age. However, similar measures of life history variation in male mate choice are lacking. We addressed this in an investigation of male mate choice in Drosophila melanogaster. We gave males the opportunity to choose a mate every day of their lives then measured variation in reproductive output. Males that were given the opportunity to choose their mates showed a subtle but significant benefit of choice during their early reproductive lives. This was negated during their late reproductive lives, however, when it was males that were given a randomly selected mate each day that fared progressively better in terms of number of offspring gained. This evidence suggests that a life history trade-off between early and late reproduction can arise in males given a regular choice of mate. We therefore identified novel age-dependent variation in the benefits of male mate choice. Our study shows the importance of considering choice in the context of life history, to gain more accurate estimates of the fitness benefits of choice.