Genetic correlation between biomass allocation to male and female functions in a natural population of Ipomopsis aggregata

Models for sex allocation assume that increased expenditure of resources on male function decreases the resources available for female function. Under some circumstances, a negative genetic correlation between investment in stamens and investment in pistil and seeds is expected. This study used a nested half-sibship design to test for genetic correlations between biomass of stamens, corolla, calyx, pistil and seeds in the hermaphroditic herb Ipomopsis aggregata. Over 5000 seeds from 32 paternal half-sib families and 229 maternal full-sib families were planted under natural field conditions and followed for up to 9 years until blooming. Stamen mass and corolla mass exhibited moderately high levels of additive genetic variance, and heritabilities of 0.32 and 0.40, respectively. Genetic correlations, as estimated with family mean correlations, were all either positive or not significantly different from zero. Even after controlling for plant size and flower number as indices of resource acquisition, paternal half-sib families that invested more biomass in stamens also invested more in the pistil and in the corolla.