Variable and sexually conflicting selection onSilene stellatafloral traits by a putative moth pollinator selective agent

Conflicting selection is an important evolutionary mechanism because it impedes directional evolution and helps to maintain phenotypic variation. It can arise when mutualistic and antagonistic selective agents exert opposing selection on the same trait and when distinct phenotypic optima are favored by different fitness components. In this study, we test for conflicting selection through different sexual functions of the hermaphroditic plant,Silene stellataduring its early and late flowering season. We find selection is consistently stronger during the early flowering season, which aligns with the activity peak of the pollinating seed predatorHadena ectypa. Importantly, we observe sex-specific selection on petal dimensions to have opposite signs. We propose that the observed sexually conflicting selection on petal design results from the negative selection through female function for the avoidance of oviposition and the subsequent fruit predation byH. ectypalarvae and the positive selection through male function for pollen export byH. ectypaadults. TheSilene-Hadenainteraction has previously been considered to be largely parasitic. Our findings suggest a trade-off mechanism that could thwart the evolution of an "escape route" from the nocturnal pollination syndrome bySilene spp. and contribute to the long-term maintenance of theSilene-Hadena system.