Conclusion
From our results, we conclude that: 1) pheromone components in H.
subflexa can evolve in response to selection independent of other
components of the sex pheromone; 2) selection need not erode the genetic
variance in order to drive this phenotypic change; 3) selection alters
the genetic correlations among pheromone components. Our study thus
shows that univariate selection responses in multicomponent sexual
signals are possible, even though pairwise genetic correlations were
high both prior to and during selection. Our study also shows that
sexual signal components can respond to selection without reductions in
genetic variance, but with rapid changes in the genetic covariance
structure. These results correspond to geographic variation in the
sexual signal found in this species and help to explain how sexual
signals in general can respond to selection without running into
constraints from indirect selection responses or depleted genetic
variation. This may be one reason why sexual signals have evolved
rapidly and repeatedly throughout the evolutionary history of animal
taxa, thereby contributing to the speciation process.