The genetic integration of sexually dimorphic traits in the dioecious plant,Silene latifolia

Abstract This chapter investigates sexual dimorphism in the dioecious, flowering plant, Silene latifolia. Results of comparisons among populations, a half-sib breeding experiment, and artificial selection on flower size indicate strong genetic integration such that selection for sexual dimorphism in any one trait affects the phenotype and extent of sexual dimorphism of many other traits. A flower size/number trade-off and the fact that larger flowers produce more ovules but not more pollen lead to selection for more (and smaller) flowers in males, but larger (and fewer) flowers in females. Strong genetic correlations between flower number and other traits are in accord with the hypothesis that the production of large numbers of flowers leads to a cost of reproduction. These results highlight the utility of taking a multi-trait, quantitative-genetic approach to understanding why the sexes differ from each other.