Data from: Evolution of reduced postcopulatory molecular interactions in Drosophila populations lacking sperm competition

In many species with internal fertilization, molecules transferred in the
male ejaculate trigger and interact with physiological changes in females.
It is controversial to what extent these interactions between the sexes
act synergistically to mediate the female switch to a reproductive state
or instead reflect sexual antagonism evolved as a byproduct of sexual
selection on males. To address this question, we eliminated sexual
selection by enforcing monogamy in populations of Drosophila melanogaster
for 65 generations and then measured the expression of male seminal fluid
protein genes and genes involved in the female response to mating. In the
absence of sperm competition, male and female reproductive interests are
perfectly aligned and any antagonism should be reduced by natural
selection. Consistent with this idea, males from monogamous populations
showed reduced expression of seminal fluid protein genes, 16% less on
average than in polygamous males. Further, we identified 428 genes that
responded to mating in females. After mating, females with an evolutionary
history of monogamy exhibited lower relative expression of genes that were
upregulated in response to mating and higher expression of genes that were
downregulated—in other words, their post-mating transcriptome appeared
more virgin-like. Surprisingly, these genes showed a similar pattern even
before mating, suggesting that monogamous females evolved to be less
poised for mating and the accompanying receipt of male seminal fluid
proteins. This reduced investment by both monogamous males and females in
molecules involved in postcopulatory interactions points to a pervasive
role of sexual conflict in shaping these interactions.