The heritability of fitness in a wild annual plant population with hierarchical size structure.

The relative magnitude of additive genetic vs. residual variation for fitness traits is important in models for predicting the rate of evolution and population persistence in response to changes in the environment. In many annual plants, lifetime reproductive fitness is correlated with end-of-season plant biomass, which can vary significantly from plant to plant in the same population. We measured end-of-season plant biomasses and obtained single nucleotide polymorphism (SNP) genotypes of plants in a dense, natural population of the annual plant species Impatiens capensis with hierarchical size structure. These data were used to estimate the amount of heritable variation for position in the size hierarchy and for plant biomass. Additive genetic variance for a position in the size hierarchy and plant biomass were both significantly different from zero. These results are discussed in relationship to the theory for the heritability of fitness in natural populations and ecological factors that potentially influence heritable variation for fitness in this species.