Abstract
Courtship song in D. melanogaster contributes substantially to male mating success through female selection. We used experimental evolution to test whether this display trait is maintained through adaptive female selection because it indicates heritable male quality for thermal stress tolerance. We used non-displaying, outbred populations of D. melanogaster (nub1) mutants and measured their rate of adaptation to a new, thermally stressful environment, relative to wild-type control populations that retained courtship song. This design retains sexually selected conflict in both treatments. Thermal stress should select across genomes for newly beneficial alleles, increasing the available genetic and phenotypic variation and, therefore, the magnitude of female benefit derived from courtship song. Following introduction to the thermally stressful environment, net reproductive rate decreased 50% over four generations, and then increased 19% over the following 16 generations. There were no differences between the treatments. Possible explanations for these results are discussed.
Highlights
The relationship between sexual fitness and population fitness is not generally understood
When natural selection was relaxed in D. serrata, sexual selection improved productivity [14]
Data is archived at http://www.csus.edu/faculty/h/holland/docs/ Puplications/Cabral.Holland.DataArchivePublic.pdf. This is the first study we know to measure the effect of a specific male courtship display on the rate adaptation to a new environment
Summary
The relationship between sexual fitness (mating and fertilization success) and population fitness (approximated by net reproductive rate) is not generally understood. Theory indicates that sexual selection can increase beneficial allele fixation [1], deleterious allele removal [1], [2,3,4], and the rate of adaptation to novel environments [5,6]. Bulb mite populations held under relaxed viability and fecundity selection showed no improvement in the presence of sexual selection [11]. Sexual selection did not increase the rate adaptation to a thermally stressful environment in D. melanogaster [16], or novel larval food resource in D. serrata [17]. Sexual selection did increase the rate of adaptation of a seed beetle to a novel host plant, yet, decreased fitness when maintained on their ancestral host [18]
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