An Experimental Test for Indirect Benefits in Drosophila melanogaster

Background: Despite much empirical attention, tests for indirect benefits of mate choice haverarely considered the major components of sexual and nonsexual offspring fitness relevant to apopulation. Here we use a novel experimental design to test for the existence of any indirectbenefits in a laboratory adapted population of D. melanogaster. Our experiment compared thefitness (mating success, longevity, and productivity) of individuals possessing genomes that derivedtwo generations previously from males that were either entirely successful (studs) or whollyunsuccessful (duds) at achieving mates in three subsequent rounds of mating trials.Results: Males from the stud treatment were 30% more successful on average at securing matesthan males from the dud treatment. In contrast, we found no difference between treatments inmeasures of productivity or of longevity when measured in a mixed-sex environment. In theabsence of females, however, males in the stud treatment outlived males in the dud treatment.Conclusion: Our results suggest that mating with successful males in this population provides anindirect benefit to females and that, at least in this environment, the benefit arises primarily throughthe production of more attractive male offspring. However, it is unclear whether this representssolely a traditional sexy sons benefit or whether there is an additional good genes component (withmale offspring simply allocating their surplus condition to traits that enhance their mating success).The lack of any detectable differences in female fitness between the two treatments suggests theformer, although the longevity advantage of males in the stud treatment when females were absentis consistent with the latter. Determining the effect of this indirect benefit on the evolution offemale mate preferences (or resistance) will require comparable data on the direct costs of matingwith various males, and an understanding of how these costs and benefits integrate acrossgenerations and vary among environments.