In Collinsia heterophylla, a mixed-mating species with delayed stigma receptivity, there is a potential for a sexual conflict over timing of stigma receptivity. Madjidian et al. use experimental crosses and perform parent–offspring regressions and sib analyses to test for heritable genetic variation and co-variation in male and female interactive traits. They find some heritable variation and evolvability in delayed stigma receptivity in the presence of pollen, but no evidence for genetic variation in the ability of pollen to fertilize ovules early. Thus the female function is more likely to respond to selection than the male function.